Consolidated Statements of Changes in Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Class A Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Balance at the beginning of the period (in shares) at Dec. 31, 2016		50,513
Balance at the beginning of the period at Dec. 31, 2016	$ 683,733	$ 51	$ 358,155	$ 325,708	$ (181)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued under stock plans, net of withholdings and related tax effects (in shares)		1,949
Common stock issued under stock plans, net of withholdings and related tax effects	6,084	$ 1	6,083
Stock-based compensation	40,734		40,734
Treasury stock acquired (in shares)		(1,326)
Repurchases of Class A common stock	(51,969)	$ (1)	(51,968)
Net income	85,887			85,887
Other comprehensive income (loss)	(549)				(549)
Balance at the end of the period (in shares) at Dec. 31, 2017		51,136
Balance at the end of the period at Dec. 31, 2017	764,550	$ 51	354,789	410,440	(730)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change and tax reform	630		1,785	(1,155)
Common stock issued under stock plans, net of withholdings and related tax effects (in shares)		1,781
Common stock issued under stock plans, net of withholdings and related tax effects	(24,127)	$ 2	(24,129)
Stock-based compensation	50,093		50,093
Net income	118,703			118,703
Other comprehensive income (loss)	593				593
Balance at the end of the period (in shares) at Dec. 31, 2018		52,917
Balance at the end of the period at Dec. 31, 2018	$ 909,812	$ 53	380,753	529,143	(137)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued under stock plans, net of withholdings and related tax effects (in shares)	70	962
Common stock issued under stock plans, net of withholdings and related tax effects	$ (14,113)	$ 1	(14,114)
Stock-based compensation	29,583		29,583
Treasury stock acquired (in shares)		(2,072)
Repurchases of Class A common stock	(100,000)	$ (2)	(99,998)
Net income	99,897			99,897
Other comprehensive income (loss)	2,177				2,177
Balance at the end of the period (in shares) at Dec. 31, 2019		51,807
Balance at the end of the period at Dec. 31, 2019	$ 927,356	$ 52	$ 296,224	$ 629,040	$ 2,040