XML 73 R58.htm IDEA: XBRL DOCUMENT v3.8.0.1
Stock Award Plans, All Plans Options and Restricted Stock Award Activity (Details) - USD ($)
$ / shares in Units, $ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Share-based Compensation Plans Combined Disclosure [Abstract]      
Intrinsic value of stock options exercised $ 1,671 $ 266 $ 2,555
Tax benefit from stock options exercised 632 100 948
Intrinsic value of restricted stock vesting 8,485 6,928 10,270
Tax benefit from restricted stock vesting 3,208 2,598 3,810
Fair value of options vested 2,530 2,495 2,180
Fair value of restricted stock vested $ 8,485 $ 6,928 $ 10,270
Fair value of stock options granted (in dollars per share) $ 20.72 $ 17.30 $ 25.18
Fair value of stock options granted $ 2,617 $ 3,231 $ 2,893
Stock Options [Member]      
Share-based Compensation Plans Combined Disclosure [Abstract]      
Unrecognized compensation cost related to unvested awards $ 3,092    
Weighted average period of recognition in years 1 year 3 months 18 days    
Fair Value Assumptions [Abstract]      
Dividend yield 0.00% 0.00% 0.00%
Average risk-free interest rate 2.00% 1.50% 1.30%
Stock price volatility 27.00% 30.00% 33.00%
Estimated option term 6 years 6 years 6 years
Restricted Stock [Member]      
Share-based Compensation Plans Combined Disclosure [Abstract]      
Unrecognized compensation cost related to unvested awards $ 16,947    
Weighted average period of recognition in years 3 years