Share-Based Compensation - Options Exercisable and Expected to Vest (Details) (USD $)	12 Months Ended
	Dec. 31, 2014
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, lower range limit (in dollars per share)	$ 3.48
Range of exercise prices, upper range limit (in dollars per share)	$ 46.97
Exercisable options, stock options, shares	3,370,351
Exercisable options, weighted average remaining contractual life	4 years 3 months 18 days
Exercisable options, weighted average exercise price (in dollars per share)	$ 14.39
Options expected to vest, stock options, shares	488,399
Options expected to vest, weighted average remaining contractual life	8 years
Options expected to vest, weighted average exercise price (in dollars per share)	$ 4.67
$3.48 to $6.16
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, lower range limit (in dollars per share)	$ 3.48
Range of exercise prices, upper range limit (in dollars per share)	$ 6.16
Exercisable options, stock options, shares	618,973
Exercisable options, weighted average remaining contractual life	6 years 7 months 6 days
Exercisable options, weighted average exercise price (in dollars per share)	$ 5.32
Options expected to vest, stock options, shares	481,243
Options expected to vest, weighted average remaining contractual life	8 years
Options expected to vest, weighted average exercise price (in dollars per share)	$ 4.61
$6.17 to $9.64
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, lower range limit (in dollars per share)	$ 6.17
Range of exercise prices, upper range limit (in dollars per share)	$ 9.64
Exercisable options, stock options, shares	475,772
Exercisable options, weighted average remaining contractual life	4 years 4 months 24 days
Exercisable options, weighted average exercise price (in dollars per share)	$ 8.66
Options expected to vest, stock options, shares	4,094
Options expected to vest, weighted average remaining contractual life	7 years 1 month 6 days
Options expected to vest, weighted average exercise price (in dollars per share)	$ 6.19
$9.65 to $19.20
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, lower range limit (in dollars per share)	$ 9.65
Range of exercise prices, upper range limit (in dollars per share)	$ 19.20
Exercisable options, stock options, shares	1,417,382
Exercisable options, weighted average remaining contractual life	4 years 9 months 18 days
Exercisable options, weighted average exercise price (in dollars per share)	$ 10.06
Options expected to vest, stock options, shares	3,062
Options expected to vest, weighted average remaining contractual life	6 years 2 months 12 days
Options expected to vest, weighted average exercise price (in dollars per share)	$ 11.31
$19.21 to $23.95
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, lower range limit (in dollars per share)	$ 19.21
Range of exercise prices, upper range limit (in dollars per share)	$ 23.95
Exercisable options, stock options, shares	9,500
Exercisable options, weighted average remaining contractual life	3 years
Exercisable options, weighted average exercise price (in dollars per share)	$ 20.20
Options expected to vest, stock options, shares	0
Options expected to vest, weighted average remaining contractual life	0 years 0 months 12 days
Options expected to vest, weighted average exercise price (in dollars per share)	$ 0.00
$23.96 to $28.70
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, lower range limit (in dollars per share)	$ 23.96
Range of exercise prices, upper range limit (in dollars per share)	$ 28.70
Exercisable options, stock options, shares	403,837
Exercisable options, weighted average remaining contractual life	2 years 4 months 24 days
Exercisable options, weighted average exercise price (in dollars per share)	$ 24.62
Options expected to vest, stock options, shares	0
Options expected to vest, weighted average remaining contractual life	0 years 0 months 12 days
Options expected to vest, weighted average exercise price (in dollars per share)	$ 0.00
$28.71 to $39.38
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, lower range limit (in dollars per share)	$ 28.71
Range of exercise prices, upper range limit (in dollars per share)	$ 39.38
Exercisable options, stock options, shares	323,487
Exercisable options, weighted average remaining contractual life	1 year 1 month 6 days
Exercisable options, weighted average exercise price (in dollars per share)	$ 35.97
Options expected to vest, stock options, shares	0
Options expected to vest, weighted average remaining contractual life	0 years 0 months 12 days
Options expected to vest, weighted average exercise price (in dollars per share)	$ 0.00
$39.39 to $41.75
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, lower range limit (in dollars per share)	$ 39.39
Range of exercise prices, upper range limit (in dollars per share)	$ 41.75
Exercisable options, stock options, shares	118,900
Exercisable options, weighted average remaining contractual life	1 year 2 months 12 days
Exercisable options, weighted average exercise price (in dollars per share)	$ 41.62
Options expected to vest, stock options, shares	0
Options expected to vest, weighted average remaining contractual life	0 years 0 months 12 days
Options expected to vest, weighted average exercise price (in dollars per share)	$ 0.00
$41.76 to $46.97
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, lower range limit (in dollars per share)	$ 41.76
Range of exercise prices, upper range limit (in dollars per share)	$ 46.97
Exercisable options, stock options, shares	2,500
Exercisable options, weighted average remaining contractual life	1 year 4 months 24 days
Exercisable options, weighted average exercise price (in dollars per share)	$ 45.76
Options expected to vest, stock options, shares	0
Options expected to vest, weighted average remaining contractual life	0 years 0 months 12 days
Options expected to vest, weighted average exercise price (in dollars per share)	$ 0.00