Employee Stock and Benefit Plans - Share Repurchase Program and 401(k) Plan (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Oct. 25, 2018	Feb. 05, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Repurchase Program, Authorized Amount				$ 100,000,000.0
Stock Repurchase Program, Additional Authorized Amount			$ 100,000,000
Stock Repurchased During Period, Value	$ 85,040,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount	115,000,000
Contributions by the Company to the 401(k) plan	$ 1,200,000	$ 1,100,000
Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Repurchased During Period, Shares	1,088,899
Stock Repurchased During Period, Value	$ 1,000