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, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Payment Arrangement [Abstract]
Total intrinsic value of stock options exercised	$ 11,733	$ 9,910	$ 25,692
Cash received from stock option exercises	5,481	4,837	8,510
Excess tax benefit from the exercise of stock options	$ 1,815	$ 1,654	$ 4,278
Number of Shares
Beginning balance (in shares)	4,319
Granted (in shares)	329
Exercised (in shares)	(442)
Forfeited/expired (in shares)	(264)
Outstanding at December 31 (in shares)	3,942	4,319
Exercisable (in shares)	1,936
Ending vested and expected to vest (in shares)	3,860
Weighted Average Exercise Price
Beginning balance (in dollars per share)	$ 34.10
Granted (in dollars per share)	39.21
Exercised (in dollars per share)	16.17
Forfeited/expired (in dollars per share)	42.37
Outstanding at December 31 (in dollars per share)	35.98	$ 34.10
Exercisable (in dollars per share)	29.38
Ending vested and expected to vest (in dollars per share)	$ 35.79
Outstanding, remaining contractual term	3 years 11 months 19 days
Exercisable, remaining contractual term	2 years 11 months 12 days
Ending vested and expected to vest, remaining contractual term	3 years 11 months 8 days
Outstanding, intrinsic value	$ 77,350
Exercisable, intrinsic value	50,678
Ending vested and expected to vest, intrinsic value	$ 76,482