Condensed 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, 2017			73,706
Beginning balance at Dec. 31, 2017		$ 1,661,914	$ 7	$ 804,731	$ 859,114	$ (1,938)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative-effect adjustment to beginning balance		3,574			3,574
Net income		144,538			144,538
Other comprehensive income (loss), net of tax		(1,688)				(1,688)
Stock-based compensation		20,851		20,851
Issuance of common stock in connection with employee equity incentive plans (in shares)			639
Issuance of common stock in connection with employee equity incentive plans		17,300	$ 1	17,299
Tax withholding paid for net share settlement of equity awards (in shares)			(7)
Tax withholding paid for net share settlement of equity awards		(1,536)		(1,536)
Vesting of early-exercised stock options		86		86
Ending balance (in shares) at Mar. 31, 2018			74,338
Ending balance at Mar. 31, 2018		1,845,039	$ 8	841,431	1,007,226	(3,626)
Beginning balance (in shares) at Dec. 31, 2018			75,668
Beginning balance at Dec. 31, 2018		2,143,389	$ 8	956,572	1,190,803	(3,994)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative-effect adjustment to beginning balance	[1]	3,702			3,702
Net income		201,029			201,029
Other comprehensive income (loss), net of tax		3,414				3,414
Stock-based compensation		24,291		24,291
Issuance of common stock in connection with employee equity incentive plans (in shares)			791
Issuance of common stock in connection with employee equity incentive plans		26,323		26,323
Tax withholding paid for net share settlement of equity awards (in shares)			(6)
Tax withholding paid for net share settlement of equity awards		(1,850)		(1,850)
Vesting of early-exercised stock options		69		69
Ending balance (in shares) at Mar. 31, 2019			76,453
Ending balance at Mar. 31, 2019		$ 2,400,367	$ 8	$ 1,005,405	$ 1,395,534	$ (580)

[1] On January 1, 2019, we adopted Accounting Standard Codification Topic 842 - Leases ("ASC 842"), which resulted in a cumulative-effect adjustment to the beginning balance of Retained Earnings for 2019. See Note 1 of the accompanying notes for further details.