Employee Stock and Benefit Plans (Options Outstanding and Vested) (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of shares, outstanding	7,039,093
Weighted average exercise price per share, outstanding (in dollar per share)	$ 7.17
Weighted average remaining contractual life, outstanding	6 years 6 months
Number of shares, vested	4,276,557
Weighted average exercise price per share, vested (in dollar per share)	$ 3.83
Stock Options
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Weighted average grant date fair value (in dollars per share)	$ 7.62	$ 4.27	$ 2.56
Grant date fair value	$ 15.2	$ 6.3	$ 4.7
Intrinsic value of options exercised	$ 11.1	$ 4.0	$ 0.8
$0.10 - $1.90
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower limit (in dollar per share)	$ 0.10
Exercise price range, upper limit (in dollar per share)	$ 1.90
Number of shares, outstanding	1,357,956
Weighted average exercise price per share, outstanding (in dollar per share)	$ 1.73
Weighted average remaining contractual life, outstanding	2 years 10 months 24 days
Number of shares, vested	1,357,956
Weighted average exercise price per share, vested (in dollar per share)	$ 1.73
$2.10 - $2.80
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower limit (in dollar per share)	$ 2.10
Exercise price range, upper limit (in dollar per share)	$ 2.80
Number of shares, outstanding	582,998
Weighted average exercise price per share, outstanding (in dollar per share)	$ 2.63
Weighted average remaining contractual life, outstanding	4 years 8 months 12 days
Number of shares, vested	582,998
Weighted average exercise price per share, vested (in dollar per share)	$ 2.63
$3.80 - $3.80
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower limit (in dollar per share)	$ 3.80
Exercise price range, upper limit (in dollar per share)	$ 3.80
Number of shares, outstanding	1,165,018
Weighted average exercise price per share, outstanding (in dollar per share)	$ 3.80
Weighted average remaining contractual life, outstanding	5 years 10 months 24 days
Number of shares, vested	879,766
Weighted average exercise price per share, vested (in dollar per share)	$ 3.80
$4.10 - $5.10
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower limit (in dollar per share)	$ 4.10
Exercise price range, upper limit (in dollar per share)	$ 5.10
Number of shares, outstanding	1,116,084
Weighted average exercise price per share, outstanding (in dollar per share)	$ 4.44
Weighted average remaining contractual life, outstanding	6 years 10 months 24 days
Number of shares, vested	916,914
Weighted average exercise price per share, vested (in dollar per share)	$ 4.37
$5.90 - $10.77
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower limit (in dollar per share)	$ 5.90
Exercise price range, upper limit (in dollar per share)	$ 10.77
Number of shares, outstanding	1,229,305
Weighted average exercise price per share, outstanding (in dollar per share)	$ 8.64
Weighted average remaining contractual life, outstanding	8 years 2 months 12 days
Number of shares, vested	399,243
Weighted average exercise price per share, vested (in dollar per share)	$ 8.06
$12.68 - $16.68
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower limit (in dollar per share)	$ 12.68
Exercise price range, upper limit (in dollar per share)	$ 16.68
Number of shares, outstanding	1,003,657
Weighted average exercise price per share, outstanding (in dollar per share)	$ 13.91
Weighted average remaining contractual life, outstanding	9 years
Number of shares, vested	129,143
Weighted average exercise price per share, vested (in dollar per share)	$ 13.24
$20.80 - $23.81
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower limit (in dollar per share)	$ 20.80
Exercise price range, upper limit (in dollar per share)	$ 23.81
Number of shares, outstanding	584,075
Weighted average exercise price per share, outstanding (in dollar per share)	$ 21.63
Weighted average remaining contractual life, outstanding	9 years 8 months 12 days
Number of shares, vested	10,537
Weighted average exercise price per share, vested (in dollar per share)	$ 20.80