Employee Stock Purchase Plan, Stock Options and Warrants - Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
Total intrinsic value of stock options exercised	$ 9,910	$ 25,692	$ 9,264
Cash received from stock option exercises	4,837	8,510	5,552
Excess tax benefit from the exercise of stock options	$ 1,654	$ 4,278	$ 2,264
Number of Shares
Beginning balance (in shares)	3,507
Granted (in shares)		1,244
Exercised (in shares)	(288)
Forfeited/expired (in shares)	(144)
Outstanding at December 31 (in shares)	4,319	3,507
Exercisable (in shares)				1,532
Ending vested and expected to vest (in shares)				4,186
Weighted Average Exercise Price
Beginning balance (in dollars per share)	$ 34.10	$ 26.30		$ 34.10
Granted (in dollars per share)		52.45
Exercised (in dollars per share)	16.48
Forfeited/expired (in dollars per share)	37.86
Outstanding at December 31 (in dollars per share)	$ 34.10	$ 26.30
Exercisable (in dollars per share)				21.98
Ending vested and expected to vest (in dollars per share)				$ 33.77
Outstanding, remaining contractual term	4 years 4 months 24 days
Exercisable, remaining contractual term	3 years 25 days
Ending vested and expected to vest, remaining contractual term	4 years 4 months 9 days
Outstanding, intrinsic value				$ 23,512
Exercisable, intrinsic value				16,403
Ending vested and expected to vest, intrinsic value				$ 23,344