Stock-Based Compensation - Narrative (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]
Share-based compensation cost	$ 8,500	$ 7,100	$ 9,200
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense	$ (1,600)	$ 2,600	3,400
Shares repurchased (in shares)	1,200,000	2,400,000
Repurchase of common stock	$ 46,580	$ 102,510	$ 112,261
Number of treasury shares retired (in shares)	3,900,000
Retirement of treasury stock	$ 0
Additional Paid-In Capital
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Retirement of treasury stock	$ 199,418
Equity Incentive Award Plan 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future issuance (in shares)	2,377,650	2,358,283