CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional paid-in capital	Accumulated other comprehensive loss	Accumulated earnings (deficit)
Balance, beginning of year at Dec. 31, 2014		$ 4	$ 838,313	$ (53)	$ (80,458)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of options and vesting of restricted stock units		1
Common stock repurchased and retired	$ (215,911)	(1)			(212,791)
Issuance of common stock upon exercise of options and vesting of restricted stock units			3,221
Stock based compensation, net of forfeitures			61,705
Accelerated share repurchase of common stock			(3,119)
Tax benefit (shortfall) of stock options			98
Unrealized gain (loss) on investments, net of tax				(15)
Unrealized gain on cash flow hedges, net of tax				0
Net income (loss)	(843)				(843)
Balance, end of year at Dec. 31, 2015	$ 606,062	$ 4	900,218	(68)	(294,092)
Balance, beginning of year (in shares) at Dec. 31, 2014		37,906,000
Number of shares
Issuance of common stock upon exercise of options and vesting of restricted stock units (in shares)		1,780,000
Common stock repurchased and retired (in shares)	(4,907,675)	(4,909,000)
Balance, end of year (in shares) at Dec. 31, 2015	34,777,000	34,777,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Impact of adoption of new accounting standard					0
Issuance of common stock upon exercise of options and vesting of restricted stock units		$ 1
Common stock repurchased and retired	$ (112,488)	(2)			(112,488)
Issuance of common stock upon exercise of options and vesting of restricted stock units			2,104
Stock based compensation, net of forfeitures			47,252
Accelerated share repurchase of common stock			0
Tax benefit (shortfall) of stock options			290
Unrealized gain (loss) on investments, net of tax				36
Unrealized gain on cash flow hedges, net of tax				0
Net income (loss)	15,906				15,906
Balance, end of year at Dec. 31, 2016	$ 559,161	$ 3	949,864	(32)	(390,674)
Number of shares
Issuance of common stock upon exercise of options and vesting of restricted stock units (in shares)		1,385,000
Common stock repurchased and retired (in shares)	(2,524,752)	(2,525,000)
Balance, end of year (in shares) at Dec. 31, 2016	33,637,000	33,637,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Impact of adoption of new accounting standard					0
Issuance of common stock upon exercise of options and vesting of restricted stock units		$ 1
Common stock repurchased and retired	$ (110,000)	(1)			(110,000)
Issuance of common stock upon exercise of options and vesting of restricted stock units			677
Stock based compensation, net of forfeitures			45,760
Accelerated share repurchase of common stock			0
Tax benefit (shortfall) of stock options			0
Unrealized gain (loss) on investments, net of tax				(27)
Unrealized gain on cash flow hedges, net of tax				1,837
Net income (loss)	30,085				30,085
Balance, end of year at Dec. 31, 2017	$ 550,724	$ 3	$ 996,301	$ 1,778	(447,358)
Number of shares
Issuance of common stock upon exercise of options and vesting of restricted stock units (in shares)		986,000
Common stock repurchased and retired (in shares)	(2,325,825)	(2,326,000)
Balance, end of year (in shares) at Dec. 31, 2017	32,297,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Impact of adoption of new accounting standard					$ 23,231