Stock-Based Compensation - Stock Options Activity (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014
Stock Options [Roll Forward]
Outstanding December 31, 2013 (shares)	5,371,538
Granted (shares)	0
Exercised (shares)	(42,032)
Canceled (shares)	(44,434)
Forfeited (shares)	(42,735)
Outstanding March 31, 2014 (shares)	5,242,337
Exercisable as of March 31, 2014 (shares)	3,577,985
Weighted Average Exercise Price [Roll Forward]
Outstanding December 31, 2013 (dollars per share)	$ 13.11
Granted (dollars per share)	$ 0.00
Exercised (dollars per share)	$ 3.99
Canceled (dollars per share)	$ 26.95
Forfeited (dollars per share)	$ 2.42
Outstanding March 31, 2014 (dollars per share)	$ 13.11
Exercisable as of March 31, 2014 (dollars per share)	$ 16.45
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options expiration term	10 years
Total unrecognized compensation expense related to non-vested stock	$ 2.0
Total compensation cost not yet recognized, period for recognition	1 year 4 months 24 days