Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Convertible notes payable	Convertible Preferred Stock	Convertible Preferred Stock	Convertible Preferred Stock Convertible Preferred Stock	Common Stock	Common Stock Convertible notes payable	Common Stock Convertible Preferred Stock	Additional Paid-In Capital	Additional Paid-In Capital Convertible notes payable	Additional Paid-In Capital Convertible Preferred Stock	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning balance (in shares) at Dec. 31, 2013				24,000,000		31,927,000
Beginning balance at Dec. 31, 2013	$ 77,732			$ 5,992		$ 3			$ 28,737			$ 42,964	$ 36
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	86,850											86,850
Other comprehensive (loss) income, net of tax	(370)												(370)
Issuance of common stock from initial public offering, net of offering costs (in shares)						6,038,000
Issuance of common stock from initial public offering, net of offering costs	239,055					$ 1			239,054
Conversion of convertible preferred stock and notes payable into common stock upon initial public offering (in shares)					(24,000,000)		1,543,000	24,000,000
Conversion of convertible preferred stock and notes payable into common stock upon initial public offering		$ 66,338	$ 0		$ (5,992)			$ 3		$ 66,338	$ 5,989
Conversion of notes payable and accrued interest, related party, into common stock upon initial public offering (in shares)							701,000
Conversion of notes payable and accrued interest, related party, into common stock upon initial public offering		$ 30,153								$ 30,153
Tax benefit for equity incentive plans	17,358								17,358
Stock-based compensation	27,619								27,619
Issuance of common stock in connection with employee equity incentive plans (in shares)						1,319,000
Issuance of common stock in connection with employee equity incentive plans	6,828								6,828
Vesting of stock options and restricted stock	4,095								4,095
Ending balance (in shares) at Dec. 31, 2014				0		65,528,000
Ending balance at Dec. 31, 2014	555,658			$ 0		$ 7			426,171			129,814	(334)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	121,102											121,102
Other comprehensive (loss) income, 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)						2,577,000
Issuance of common stock in connection with employee equity incentive plans	27,201								27,201
Vesting of stock options and restricted stock (in shares)						27,000
Vesting of stock options and restricted stock	2,226								2,226
Ending balance (in shares) at Dec. 31, 2015				0		68,132,000
Ending balance at Dec. 31, 2015	788,152			$ 0		$ 7			537,904			250,916	(675)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	184,189											184,189
Other comprehensive (loss) income, 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)						2,694,000
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)						(15,000)
Minimum tax withholding paid for net share settlement of equity awards	(1,100)								(1,100)
Vesting of stock options and restricted stock	1,082								1,082
Ending balance (in shares) at Dec. 31, 2016				0		70,811,000
Ending balance at Dec. 31, 2016	$ 1,107,820			$ 0		$ 7			$ 674,183			$ 435,105	$ (1,475)