Stock-based Compensation (Stock Option Activity) (Details) (Stock Options [Member], USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding, beginning of period (number of options)	6,133	7,904	7,796
Grants (number of options)	922	1,521	1,751
Exercises (number of options)	(326)	(708)	(1,167)
Early exercised options repurchased (number of options)			(476)
Forfeited/Cancelled (number of options)	(2,603)	(2,584)	0
Outstanding, end of period (number of options)	4,126	6,133	7,904	7,796
Options Vested and Expected to Vest (shares)	4,006
Options Exercisable (number of options)	2,805
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Outstanding, beginning of period, weighted average exercise price per share (dollars per option)	$ 6.65	$ 7.35	$ 6.27
Grants, weighted average exercise price per share (dollars per option)	$ 2.28	$ 3.42	$ 9.33
Exercises, weighted average exercise price per share (dollars per option)	$ 0.98	$ 1.78	$ 2.21
Early exercised option repurchased, weighted average exercise price per share (dollars per option)			$ 9.51
Forfeited/Cancelled, weighted average exercise price per share (dollars per option)	$ 7.35	$ 8.23	$ 0.00
Outstanding, end of period, weighted average exercise price per share (dollars per option)	$ 5.68	$ 6.65	$ 7.35	$ 6.27
Options Vested and Expected to Vest (dollars per option)	$ 5.77
Options Exercisable (dollars per option)	$ 6.76
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Options Outstanding, Weighted Average Remaining Contractual Terms (years)	5 years 9 months	4 years 10 months 27 days	6 years 9 months 7 days	6 years 6 months 25 days
Options Outstanding, Aggregate Intrinsic Value	$ 87	$ 657	$ 6,570	$ 34,228
Options Exercised, Aggregate Intrinsic Value	409	925	9,077
Options Vested and Expected to Vest, Weighted Average Remaining Contractual Term (years)	5 years 7 months 27 days
Options Vested and Expected to Vest, Aggregate Intrinsic Value	87
Options Exercisable, Weighted Average Remaining Contractual Terms (years)	4 years 4 months 13 days
Options Exercisable, Aggregate Intrinsic Value	$ 87