CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Retained Earnings
Balance (in shares) at Dec. 31, 2012		28,348
Balance at Dec. 31, 2012	$ 826,343	$ 283	$ 792,988	$ (6,518)	$ 39,590
Net income (loss)	29,734				29,734
Foreign currency translation adjustment	610			610
Net decrease in unrealized loss on investments	378			378
Exercise of stock options (in shares)		409
Exercise of stock options	16,823	$ 3	16,820
Restricted stock grants (in shares)		238
Restricted stock grants	0	$ 2
Restricted stock grants adjustments			(2)
Restricted stock grants surrendered (in shares)		(158)
Restricted stock grants surrendered	(8,469)	$ 0	(8,469)
Stock compensation expense, net of forfeitures	41,403		41,403
Employee stock purchase plan (in shares)		11
Employee stock purchase plan	1,455		1,455
Excess tax benefit from stock-based compensation	19,585		19,585
Balance (in shares) at Dec. 31, 2013		28,848
Balance at Dec. 31, 2013	927,862	$ 288	863,780	(5,530)	69,324
Net income (loss)	44,869				44,869
Foreign currency translation adjustment	(1,690)			(1,690)
Net decrease in unrealized loss on investments	836			836
Exercise of stock options (in shares)		68
Exercise of stock options	3,803	$ 1	3,802
Restricted stock grants (in shares)		260
Restricted stock grants	0	$ 2
Restricted stock grants adjustments			(2)
Restricted stock grants surrendered (in shares)		(321)
Restricted stock grants surrendered	(50,555)	$ (2)	(50,553)
Stock compensation expense, net of forfeitures	28,503		28,503
Stock issued for equity offering (in shares)		3,450
Stock issued for equity offering	529,360	$ 34	529,326
Employee stock purchase plan (in shares)		13
Employee stock purchase plan	2,152		2,152
Excess tax benefit from stock-based compensation	28,406		28,406
Balance (in shares) at Dec. 31, 2014		32,318
Balance at Dec. 31, 2014	1,513,546	$ 323	1,405,414	(6,384)	114,193
Net income (loss)	(3,465)				(3,465)
Foreign currency translation adjustment	(1,466)			(1,466)
Net decrease in unrealized loss on investments	256			256
Exercise of stock options (in shares)		60
Exercise of stock options	5,069	$ 1	5,068
Restricted stock grants (in shares)		239
Restricted stock grants	0	$ 2
Restricted stock grants adjustments			(2)
Restricted stock grants surrendered (in shares)		(121)
Restricted stock grants surrendered	(16,436)	$ (1)	(16,435)
Stock compensation expense, net of forfeitures	35,153		35,153
Employee stock purchase plan (in shares)		13
Employee stock purchase plan	2,595		2,595
Excess tax benefit from stock-based compensation	8,528		8,528
Balance (in shares) at Dec. 31, 2015		32,509
Balance at Dec. 31, 2015	$ 1,543,780	$ 325	$ 1,440,321	$ (7,594)	$ 110,728