Stockholders' Equity (Deficit) and Stock-Based Compensation - Options Outstanding and Exercisable (Details) (USD $) | 9 Months Ended | 12 Months Ended |
In Thousands, except Per Share data, unless otherwise specified | Sep. 30, 2014 | Dec. 31, 2013 |
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] | ' | ' |
Outstanding at June 30, 2014 (shares) | 27,518 | 26,724 |
Options outstanding at June 30, 2014 - Weighted-average remaining contractual term | '7 years 4 months 17 days | '7 years 6 months 18 days |
Options outstanding at June 30, 2014 - Weighted average exercise price (in US$ per share) | $5.79 | $2.47 |
Options exercisable (shares) | 19,356 | ' |
Options exercisable - Weighted average exercise price (in US$ per share) | $1.49 | ' |
$ 0.18–0.66 | ' | ' |
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] | ' | ' |
Range of exercise prices - Lower limit (in US$ per share) | $0.18 | ' |
Range of exercise prices - Upper limit (in US$ per share | $0.66 | ' |
Outstanding at June 30, 2014 (shares) | 8,901 | ' |
Options outstanding at June 30, 2014 - Weighted-average remaining contractual term | '6 years 4 months 13 days | ' |
Options outstanding at June 30, 2014 - Weighted average exercise price (in US$ per share) | $0.62 | ' |
Options exercisable (shares) | 8,814 | ' |
Options exercisable - Weighted average exercise price (in US$ per share) | $0.62 | ' |
0.76 | ' | ' |
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] | ' | ' |
Range of exercise prices - Lower limit (in US$ per share) | $0.76 | ' |
Range of exercise prices - Upper limit (in US$ per share | $0.76 | ' |
Outstanding at June 30, 2014 (shares) | 8,712 | ' |
Options outstanding at June 30, 2014 - Weighted-average remaining contractual term | '6 years 8 months 19 days | ' |
Options outstanding at June 30, 2014 - Weighted average exercise price (in US$ per share) | $0.76 | ' |
Options exercisable (shares) | 8,310 | ' |
Options exercisable - Weighted average exercise price (in US$ per share) | $0.76 | ' |
1.52–2.96 | ' | ' |
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] | ' | ' |
Range of exercise prices - Lower limit (in US$ per share) | $1.52 | ' |
Range of exercise prices - Upper limit (in US$ per share | $2.96 | ' |
Outstanding at June 30, 2014 (shares) | 1,767 | ' |
Options outstanding at June 30, 2014 - Weighted-average remaining contractual term | '7 years 3 months 22 days | ' |
Options outstanding at June 30, 2014 - Weighted average exercise price (in US$ per share) | $1.91 | ' |
Options exercisable (shares) | 1,147 | ' |
Options exercisable - Weighted average exercise price (in US$ per share) | $1.87 | ' |
8.3 | ' | ' |
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] | ' | ' |
Range of exercise prices - Lower limit (in US$ per share) | $8.30 | ' |
Range of exercise prices - Upper limit (in US$ per share | $8.30 | ' |
Outstanding at June 30, 2014 (shares) | 504 | ' |
Options outstanding at June 30, 2014 - Weighted-average remaining contractual term | '8 years 18 days | ' |
Options outstanding at June 30, 2014 - Weighted average exercise price (in US$ per share) | $8.30 | ' |
Options exercisable (shares) | 243 | ' |
Options exercisable - Weighted average exercise price (in US$ per share) | $8.30 | ' |
13.72 | ' | ' |
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] | ' | ' |
Range of exercise prices - Lower limit (in US$ per share) | $13.72 | ' |
Range of exercise prices - Upper limit (in US$ per share | $13.72 | ' |
Outstanding at June 30, 2014 (shares) | 871 | ' |
Options outstanding at June 30, 2014 - Weighted-average remaining contractual term | '8 years 4 months 24 days | ' |
Options outstanding at June 30, 2014 - Weighted average exercise price (in US$ per share) | $13.72 | ' |
Options exercisable (shares) | 347 | ' |
Options exercisable - Weighted average exercise price (in US$ per share) | $13.72 | ' |
15.4 | ' | ' |
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] | ' | ' |
Range of exercise prices - Lower limit (in US$ per share) | $15.40 | ' |
Range of exercise prices - Upper limit (in US$ per share | $15.40 | ' |
Outstanding at June 30, 2014 (shares) | 572 | ' |
Options outstanding at June 30, 2014 - Weighted-average remaining contractual term | '8 years 8 months 9 days | ' |
Options outstanding at June 30, 2014 - Weighted average exercise price (in US$ per share) | $15.40 | ' |
Options exercisable (shares) | 204 | ' |
Options exercisable - Weighted average exercise price (in US$ per share) | $15.40 | ' |
15.59 | ' | ' |
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] | ' | ' |
Range of exercise prices - Lower limit (in US$ per share) | $15.59 | ' |
Range of exercise prices - Upper limit (in US$ per share | $15.59 | ' |
Outstanding at June 30, 2014 (shares) | 431 | ' |
Options outstanding at June 30, 2014 - Weighted-average remaining contractual term | '8 years 10 months 24 days | ' |
Options outstanding at June 30, 2014 - Weighted average exercise price (in US$ per share) | $15.59 | ' |
Options exercisable (shares) | 122 | ' |
Options exercisable - Weighted average exercise price (in US$ per share) | $15.59 | ' |
16.19 | ' | ' |
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] | ' | ' |
Range of exercise prices - Lower limit (in US$ per share) | $16.19 | ' |
Range of exercise prices - Upper limit (in US$ per share | $16.19 | ' |
Outstanding at June 30, 2014 (shares) | 761 | ' |
Options outstanding at June 30, 2014 - Weighted-average remaining contractual term | '9 years 1 month 21 days | ' |
Options outstanding at June 30, 2014 - Weighted average exercise price (in US$ per share) | $16.19 | ' |
Options exercisable (shares) | 13 | ' |
Options exercisable - Weighted average exercise price (in US$ per share) | $16.19 | ' |
16.22 | ' | ' |
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] | ' | ' |
Range of exercise prices - Lower limit (in US$ per share) | $16.22 | ' |
Range of exercise prices - Upper limit (in US$ per share | $16.22 | ' |
Outstanding at June 30, 2014 (shares) | 1,125 | ' |
Options outstanding at June 30, 2014 - Weighted-average remaining contractual term | '9 years 3 months 29 days | ' |
Options outstanding at June 30, 2014 - Weighted average exercise price (in US$ per share) | $16.22 | ' |
Options exercisable (shares) | 0 | ' |
Options exercisable - Weighted average exercise price (in US$ per share) | $0 | ' |
16.39 | ' | ' |
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] | ' | ' |
Range of exercise prices - Lower limit (in US$ per share) | $16.39 | ' |
Range of exercise prices - Upper limit (in US$ per share | $16.39 | ' |
Outstanding at June 30, 2014 (shares) | 651 | ' |
Options outstanding at June 30, 2014 - Weighted-average remaining contractual term | '9 years 6 months 7 days | ' |
Options outstanding at June 30, 2014 - Weighted average exercise price (in US$ per share) | $16.39 | ' |
Options exercisable (shares) | 14 | ' |
Options exercisable - Weighted average exercise price (in US$ per share) | $16.39 | ' |
18.4 | ' | ' |
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] | ' | ' |
Range of exercise prices - Lower limit (in US$ per share) | $18.40 | ' |
Range of exercise prices - Upper limit (in US$ per share | $18.40 | ' |
Outstanding at June 30, 2014 (shares) | 2,800 | ' |
Options outstanding at June 30, 2014 - Weighted-average remaining contractual term | '9 years 8 months 5 days | ' |
Options outstanding at June 30, 2014 - Weighted average exercise price (in US$ per share) | $18.40 | ' |
Options exercisable (shares) | 142 | ' |
Options exercisable - Weighted average exercise price (in US$ per share) | $18.40 | ' |
38.84-41.98 | ' | ' |
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] | ' | ' |
Range of exercise prices - Lower limit (in US$ per share) | $38.84 | ' |
Range of exercise prices - Upper limit (in US$ per share | $41.98 | ' |
Outstanding at June 30, 2014 (shares) | 192 | ' |
Options outstanding at June 30, 2014 - Weighted-average remaining contractual term | '9 years 9 months 22 days | ' |
Options outstanding at June 30, 2014 - Weighted average exercise price (in US$ per share) | $40.85 | ' |
Options exercisable (shares) | 0 | ' |
Options exercisable - Weighted average exercise price (in US$ per share) | $0 | ' |
43.96-65.23 | ' | ' |
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] | ' | ' |
Range of exercise prices - Lower limit (in US$ per share) | $43.96 | ' |
Range of exercise prices - Upper limit (in US$ per share | $65.23 | ' |
Outstanding at June 30, 2014 (shares) | 231 | ' |
Options outstanding at June 30, 2014 - Weighted-average remaining contractual term | '9 years 10 months 2 days | ' |
Options outstanding at June 30, 2014 - Weighted average exercise price (in US$ per share) | $49.40 | ' |
Options exercisable (shares) | 0 | ' |
Options exercisable - Weighted average exercise price (in US$ per share) | $0 | ' |
0.18-65.23 | ' | ' |
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] | ' | ' |
Range of exercise prices - Lower limit (in US$ per share) | $0.18 | ' |
Range of exercise prices - Upper limit (in US$ per share | $65.23 | ' |