Stock-Based Compensation - Stock Options by Exercise Price (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	9 Months Ended
	Sep. 30, 2014
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of Shares Underlying Outstanding Options (in shares)	13,977
Weighted- Average Remaining Contractual Life (Years)	8 years 4 months 24 days
Weighted- Average Exercise Price per Share (usd per share)	$ 13.25
Number of Shares Underlying Outstanding Options (in shares)	3,661
Weighted- Average Exercise Price per Share (usd per share)	$ 4.67
$3.33 - $4.16
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Upper Range Limit	$ 4.16
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Lower Range Limit	$ 3.33
Number of Shares Underlying Outstanding Options (in shares)	4,076
Weighted- Average Remaining Contractual Life (Years)	7 years 2 months 27 days
Weighted- Average Exercise Price per Share (usd per share)	$ 3.65
Number of Shares Underlying Outstanding Options (in shares)	2,463
Weighted- Average Exercise Price per Share (usd per share)	$ 3.60
$4.18 - $4.92
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Upper Range Limit	$ 4.92
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Lower Range Limit	$ 4.18
Number of Shares Underlying Outstanding Options (in shares)	2,123
Weighted- Average Remaining Contractual Life (Years)	8 years 1 month 6 days
Weighted- Average Exercise Price per Share (usd per share)	$ 4.56
Number of Shares Underlying Outstanding Options (in shares)	618
Weighted- Average Exercise Price per Share (usd per share)	$ 4.73
$7.76 - $8.77
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Upper Range Limit	$ 8.77
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Lower Range Limit	$ 7.76
Number of Shares Underlying Outstanding Options (in shares)	1,971
Weighted- Average Remaining Contractual Life (Years)	8 years 7 months 6 days
Weighted- Average Exercise Price per Share (usd per share)	$ 8.26
Number of Shares Underlying Outstanding Options (in shares)	447
Weighted- Average Exercise Price per Share (usd per share)	$ 8.29
$10.18
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Upper Range Limit	$ 10.18
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Lower Range Limit	$ 10.18
Number of Shares Underlying Outstanding Options (in shares)	1,886
Weighted- Average Remaining Contractual Life (Years)	8 years 11 months 19 days
Weighted- Average Exercise Price per Share (usd per share)	$ 10.18
Number of Shares Underlying Outstanding Options (in shares)	120
Weighted- Average Exercise Price per Share (usd per share)	$ 10.18
$22.49
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Upper Range Limit	$ 22.49
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Lower Range Limit	$ 22.49
Number of Shares Underlying Outstanding Options (in shares)	1,041
Weighted- Average Remaining Contractual Life (Years)	9 years 2 months 23 days
Weighted- Average Exercise Price per Share (usd per share)	$ 22.49
Number of Shares Underlying Outstanding Options (in shares)	4
Weighted- Average Exercise Price per Share (usd per share)	$ 22.49
$30.67
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Upper Range Limit	$ 30.67
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Lower Range Limit	$ 30.67
Number of Shares Underlying Outstanding Options (in shares)	1,658
Weighted- Average Remaining Contractual Life (Years)	9 years 4 months 10 days
Weighted- Average Exercise Price per Share (usd per share)	$ 30.67
Number of Shares Underlying Outstanding Options (in shares)	2
Weighted- Average Exercise Price per Share (usd per share)	$ 30.47
$34.12 - $38.00
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Upper Range Limit	$ 38
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Lower Range Limit	$ 34.12
Number of Shares Underlying Outstanding Options (in shares)	1,072
Weighted- Average Remaining Contractual Life (Years)	9 years 6 months 26 days
Weighted- Average Exercise Price per Share (usd per share)	$ 36.92
Number of Shares Underlying Outstanding Options (in shares)	7
Weighted- Average Exercise Price per Share (usd per share)	$ 35.26
$75.00 - $84.00
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Upper Range Limit	$ 84
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Lower Range Limit	$ 75
Number of Shares Underlying Outstanding Options (in shares)	150
Weighted- Average Remaining Contractual Life (Years)	9 years 10 months 21 days
Weighted- Average Exercise Price per Share (usd per share)	$ 75.60
Number of Shares Underlying Outstanding Options (in shares)	0
Weighted- Average Exercise Price per Share (usd per share)	$ 0