Stock-based Compensation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Shares
Outstanding at beginning of period	3,212
Granted	0
Exercised	(959)
Forfeited	(97)
Outstanding at end of period	2,156	3,212
Exercisable at end of period	1,970
Vested and expected to vest at end of period	2,147
Weighted-Average Exercise Price
Outstanding at beginning of period	$ 29.66
Granted	0.00
Exercised	29.47
Forfeited	31.16
Outstanding at end of period	29.67	$ 29.66
Exercisable at end of period	29.28
Vested and expected to vest at end of period	$ 29.66
Weighted-Average Remaining Contractual Term (in years)
Outstanding at beginning of period	4 years 8 months 15 days	5 years 5 months 4 days
Exercisable at end of period	4 years 5 months 2 days
Vested and expected to vest at end of period	4 years 8 months 15 days
Outstanding at end of period	4 years 8 months 15 days	5 years 5 months 4 days
Aggregate Intrinsic Value
Outstanding at end of period	$ 29,903
Exercisable at end of period	28,091
Vested and expected to vest at end of period	$ 29,812