Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands		Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning balance (in shares) at Dec. 31, 2014			65,528
Beginning balance at Dec. 31, 2014		$ 555,658	$ 7	$ 426,171	$ 129,814	$ (334)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		121,102			121,102
Other comprehensive loss, net of tax		(341)				(341)
Tax benefit for equity incentive plans		37,003		37,003
Stock-based compensation		45,303		45,303
Issuance of common stock in connection with employee equity incentive plans (in shares)			2,577
Issuance of common stock in connection with employee equity incentive plans		27,201		27,201
Vesting of early exercised stock options and restricted stock (in shares)			27
Vesting of early exercised stock options and restricted stock		2,226		2,226
Ending balance (in shares) at Dec. 31, 2015			68,132
Ending balance at Dec. 31, 2015		788,152	$ 7	537,904	250,916	(675)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		184,189			184,189
Other comprehensive loss, net of tax		(800)				(800)
Tax benefit for equity incentive plans		42,084		42,084
Stock-based compensation		59,032		59,032
Issuance of common stock in connection with employee equity incentive plans (in shares)			2,694
Issuance of common stock in connection with employee equity incentive plans		35,181		35,181
Minimum tax withholding paid for net share settlement of equity awards (in shares)			(15)
Minimum tax withholding paid for net share settlement of equity awards		(1,100)		(1,100)
Vesting of early exercised stock options and restricted stock		1,082		1,082
Ending balance (in shares) at Dec. 31, 2016			70,811
Ending balance at Dec. 31, 2016		1,107,820	$ 7	674,183	435,105	(1,475)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative-effect adjustment to beginning balance	[1]	2,279		1,471	808	0
Net income		423,201			423,201
Other comprehensive loss, net of tax		(463)				(463)
Stock-based compensation		75,427		75,427
Issuance of common stock in connection with employee equity incentive plans (in shares)			2,918
Issuance of common stock in connection with employee equity incentive plans		57,111		57,111
Minimum tax withholding paid for net share settlement of equity awards (in shares)			(23)
Minimum tax withholding paid for net share settlement of equity awards		(4,025)		(4,025)
Vesting of early exercised stock options and restricted stock		564		564
Ending balance (in shares) at Dec. 31, 2017			73,706
Ending balance at Dec. 31, 2017		$ 1,661,914	$ 7	$ 804,731	$ 859,114	$ (1,938)

[1] During our first fiscal quarter of 2017, we adopted Accounting Standards Update 2016-09, "Compensation-Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting." Refer to Note 1 - Recently Adopted Accounting Pronouncements for further details. This adoption resulted in a cumulative-effect adjustment to the beginning balance of Additional Paid-in Capital and Retained Earnings, respectively, for 2017.