Quarterly report pursuant to Section 13 or 15(d)

Stock-Based Compensation (Details 2)

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Stock-Based Compensation (Details 2) (USD $)
3 Months Ended 6 Months Ended
Jun. 30, 2014
Jun. 30, 2013
Jun. 30, 2014
Jun. 30, 2013
Summary of weighted average assumptions used to value options granted        
Grant date fair value of stock options (in dollars per share)     $ 16.81 $ 6.11
Volatility (as a percent)     38.70% 40.40%
Risk-free interest rate (as a percent)     1.80% 1.00%
Dividend yield (as a percent) 0.00% 0.00% 0.00% 0.00%
Expected term     6 years 6 years