CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Common Stock [Member]	Additional Paid in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Deficit [Member]	Total
Balance at Dec. 31, 2012	$ 102	$ 1,077,150	$ 12,480	$ (906,966)	$ 182,766
Balance (in shares) at Dec. 31, 2012	101,481
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	$ 0	0	0	(60,644)	(60,644)
Change in unrealized gains (losses), net of tax	0	0	8,600	0	8,600
Issuance of common stock in connection with employee stock plans	$ 5	62,953	0	0	62,958
Issuance of common stock in connection with employee stock plans (in shares)	5,372
Issuance of public common stock	$ 9	173,283	0	0	173,292
Issuance of public common stock (in shares)	9,618
Share-based compensation expense	$ 0	11,418	0	0	11,418
Balance at Dec. 31, 2013	$ 116	1,324,804	21,080	(967,610)	378,390
Balance (in shares) at Dec. 31, 2013	116,471
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	$ 0	0	0	(38,984)	(38,984)
Change in unrealized gains (losses), net of tax	0	0	18,667	0	18,667
Issuance of common stock in connection with employee stock plans	$ 2	23,071	0	0	23,073
Issuance of common stock in connection with employee stock plans (in shares)	1,972
2 3/4 percent convertible senior notes redemption, equity portion	$ 0	(326,444)	0	0	(326,444)
1 percent convertible senior notes, equity portion, net of issuance costs	0	170,232	0	0	170,232
Share-based compensation expense	0	31,383	0	0	31,383
Excess tax benefits from shared-based compensation awards	0	1,463	0	0	1,463
Balance at Dec. 31, 2014	$ 118	1,224,509	39,747	(1,006,594)	257,780
Balance (in shares) at Dec. 31, 2014	118,443
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	$ 0	0	0	(88,278)	(88,278)
Change in unrealized gains (losses), net of tax	0	0	(53,312)	0	(53,312)
Issuance of common stock in connection with employee stock plans	$ 2	24,888	0	0	24,890
Issuance of common stock in connection with employee stock plans (in shares)	1,908
Share-based compensation expense	$ 0	59,314	0	0	59,314
Excess tax benefits from shared-based compensation awards	0	396	0	0	396
Balance at Dec. 31, 2015	$ 120	$ 1,309,107	$ (13,565)	$ (1,094,872)	$ 200,790
Balance (in shares) at Dec. 31, 2015	120,351