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Stock-Based Awards - Stock Option Information (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Compensation expense recognized $ 65,830 $ 54,699 $ 43,081
Stock options      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Total intrinsic value of options exercised 9,200 18,200 11,400
Total grant date fair value of stock options vested 15,400 24,300 32,300
Compensation expense recognized 14,000 23,000 28,000
Unrecognized compensation expense related to options $ 5,400    
Unrecognized compensation expense, weighted-average period of recognition 1 year    
Aggregate grant date fair value of stock options granted   $ 1,800 $ 8,400