Quarterly report pursuant to Section 13 or 15(d)

Debt (Credit Agreement) (Details)

v3.10.0.1
Debt (Credit Agreement) (Details) - Second Amended and Restated Credit Agreement - USD ($)
9 Months Ended
Sep. 30, 2018
Jul. 31, 2017
Debt    
Credit facility amount   $ 350,000,000
Right to increase credit facility, amount   $ 50,000,000
Minimum | LIBOR    
Debt    
Spread on variable rate basis (as a percent) 1.50%  
Maximum | LIBOR    
Debt    
Spread on variable rate basis (as a percent) 3.25%