Common Stock (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended					9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Equity, Class of Treasury Stock [Line Items]
Repurchase of common stock	$ 0	$ 30,000	$ 5,937	$ 0	$ 43,525
2018 Program [Member]
Equity, Class of Treasury Stock [Line Items]
Stock Repurchase Program, Authorized Amount	150,000					$ 150,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 98,720					$ 98,720
Open Market [Member]
Equity, Class of Treasury Stock [Line Items]
Treasury Stock Acquired, Average Cost Per Share						$ 69.85	$ 122.64
Repurchase of common stock (shares)						85,000	69,503
Repurchase of common stock						$ 5,937	$ 8,524
ASR [Member]
Equity, Class of Treasury Stock [Line Items]
Treasury Stock Acquired, Average Cost Per Share						$ 42.91	$ 135.51
Repurchase of common stock (shares)	72,875	626,305		51,092	207,193	699,180	258,285
Repurchase of common stock	$ 30,000			$ 35,000