Stock-Based Compensation (Tables)
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12 Months Ended |
Dec. 31, 2017 |
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| Stock-Based Compensation |
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| Schedule of stock-based compensation expense |
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Year Ended December 31,
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2017
|
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2016
|
|
2015
|
|
Stock-based compensation expense
|
|
$
|
31,331
|
|
$
|
33,276
|
|
$
|
15,161
|
|
Tax effect on stock-based compensation expense
|
|
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(11,906)
|
|
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(13,001)
|
|
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(7,678)
|
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Net effect on income
|
|
$
|
19,425
|
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$
|
20,275
|
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$
|
7,483
|
|
| Schedule of weighted average assumptions used to value options granted |
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At December 31,
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2017
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2016
|
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2015
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Grant date fair value of options
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$
|
14.51
|
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$
|
9.56
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$
|
19.06
|
|
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Volatility
|
|
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43.8
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%
|
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42.2
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%
|
|
37.8
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%
|
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Risk-free interest rate
|
|
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2.1
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%
|
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1.4
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%
|
|
1.8
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%
|
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Dividend yield
|
|
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—
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%
|
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—
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%
|
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—
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%
|
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Expected term (in years)
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|
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6.3
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|
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6.3
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6.0
|
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| Summary of option activity under the Company's plans |
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Weighted-Average
|
|
|
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Weighted-
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Remaining
|
|
|
|
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|
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Average
|
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Contractual Life
|
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Aggregate
|
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Options
|
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Exercise Price
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(Years)
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Intrinsic Value
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Outstanding as of December 31, 2014
|
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4,265,337
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$
|
10.73
|
|
4.7
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$
|
163,830
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Granted
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358,087
|
|
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48.38
|
|
|
|
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Exercised
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(1,047,911)
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|
|
7.90
|
|
|
|
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Forfeited
|
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(41,722)
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|
|
41.10
|
|
|
|
|
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Outstanding as of December 31, 2015
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3,533,791
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|
|
15.03
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|
4.7
|
|
|
61,199
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Granted
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163,864
|
|
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22.38
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|
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Exercised
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(598,382)
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8.23
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|
|
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Forfeited
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(66,079)
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|
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35.08
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Outstanding as of December 31, 2016
|
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3,033,194
|
|
|
16.33
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|
4.3
|
|
|
63,264
|
|
Granted
|
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75,238
|
|
|
31.70
|
|
|
|
|
|
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Exercised
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(837,857)
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|
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9.49
|
|
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Forfeited
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(16,010)
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|
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37.42
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|
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|
|
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Outstanding as of December 31, 2017
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2,254,565
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19.23
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4.3
|
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|
69,939
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Options exercisable
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2,041,660
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17.74
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3.8
|
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|
66,291
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| Schedule of other information |
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Year Ended December 31,
|
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2017
|
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2016
|
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2015
|
|
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Total intrinsic value of options exercised
|
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$
|
29,562
|
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$
|
14,165
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$
|
37,879
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Cash received from exercises of stock options
|
|
|
7,951
|
|
|
4,924
|
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|
8,279
|
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| Summary of the activity for unvested restricted stock units and awards granted under the Company's plans |
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Weighted-
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Average Grant
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Number of
|
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Date Fair Value
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Shares
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per Share
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Outstanding as of December 31, 2014
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1,098,674
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$
|
33.72
|
|
Granted
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1,508,796
|
|
|
34.55
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Vested
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(434,292)
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|
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29.26
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Forfeited
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(19,967)
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|
38.58
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Outstanding as of December 31, 2015
|
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2,153,211
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|
|
35.63
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Granted
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1,009,661
|
|
|
28.82
|
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Vested
|
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(1,082,206)
|
|
|
29.12
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Forfeited
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(185,907)
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|
30.96
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Outstanding as of December 31, 2016
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1,894,759
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|
|
30.40
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Granted
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959,591
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|
|
32.38
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Vested
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(969,513)
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|
|
31.51
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Forfeited
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(118,198)
|
|
|
30.11
|
|
Outstanding as of December 31, 2017
|
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1,766,639
|
|
|
32.48
|
|