Equity - Stock Incentive Plans (Details) | 6 Months Ended |
Jun. 30, 2016USD ($)plan$ / sharesshares | Jun. 30, 2015 |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | | |
Number of share-based compensation plans | plan | 4 | |
Number of shares [Roll forward] | | |
Outstanding, beginning of period (in shares) | shares | 14,019,629 | |
Granted (in shares) | shares | 0 | |
Exercised (in shares) | shares | (804,041) | |
Unvested options forfeited (in shares) | shares | (79,810) | |
Vested options expired (in shares) | shares | (29,191) | |
Outstanding, end of period (in shares) | shares | 13,106,587 | |
Vested at end of period (in shares) | shares | 11,710,880 | |
Exercisable options, vested and expected to vest (in shares) | shares | 13,047,941 | |
Weighted-Average Exercise Price [Roll forward] | | |
Outstanding, weighted average exercise price, beginning of period (in dollars per share) | $ 3.62 | |
Granted, weighted average exercise price (in dollars per share) | 0 | |
Exercised, weighted average exercise price (in dollars per share) | 2.51 | |
Unvested options forfeited, weighted-average exercise price (in dollars per share) | 6.44 | |
Vested options expired, weighted-average exercise price (in dollars per share) | 6.44 | |
Outstanding, weighted average exercise price, end of period (in dollars per share) | 3.67 | |
Vested at end of period, weighted average exercise price (in dollars per share) | 3.27 | |
Vested and expected to vest, weighted average exercise price (in dollars per share) | $ 3.66 | |
Stock options, additional disclosures [Abstract] | | |
Outstanding Options, weighted average remaining contractual term (in years) | 6 years | |
Vested at end of period, weighted average remaining contractual term (in years) | 5 years 9 months 18 days | |
Vested and expected to vest, weighted average remaining contractual term (in years) | 6 years | |
Outstanding, aggregate intrinsic value | $ | $ 56,844,050 | |
Vested at end of period, aggregate intrinsic value | $ | 55,362,178 | |
Vested or expected to vest, aggregate intrinsic value | $ | 56,809,041 | |
Exercised options, intrinsic value | $ | $ 4,937,922 | |
Number of outstanding options (in shares) | shares | 13,106,587 | |
Outstanding Options, weighted average remaining contractual term (in years) | 6 years | |
Outstanding Options, weighted average exercise price (in dollars per share) | $ 3.67 | |
Number of exercisable options (in shares) | shares | 11,730,880 | |
Exercisable Options, weighted average exercise price (in dollars per share) | $ 3.27 | |
Total unrecognized compensation expense | $ | $ 3,283,152 | |
Fair value options valuation assumptions [Abstract] | | |
Expected volatility Minimum | | 54.40% |
Expected volatility Maximum | | 58.10% |
Expected life (in years) | | 6 years |
Expected dividend yield | | 0.00% |
Risk-free interest rate Minimum | | 1.51% |
Risk-free interest rate Maximum | | 1.68% |
$0.50 - $0.76 | | |
Stock options, additional disclosures [Abstract] | | |
Outstanding Options, weighted average remaining contractual term (in years) | 2 years 10 months 24 days | |
Exercise Price Range, lower range limit (in dollars per share) | $ 0.50 | |
Exercise Price Range, upper range limit (in dollars per share) | $ 0.76 | |
Number of outstanding options (in shares) | shares | 441,429 | |
Outstanding Options, weighted average remaining contractual term (in years) | 2 years 10 months 24 days | |
Outstanding Options, weighted average exercise price (in dollars per share) | $ 0.72 | |
Number of exercisable options (in shares) | shares | 441,429 | |
Exercisable Options, weighted average exercise price (in dollars per share) | $ 0.72 | |
$0.87 - $1.35 | | |
Stock options, additional disclosures [Abstract] | | |
Outstanding Options, weighted average remaining contractual term (in years) | 5 years 2 months 12 days | |
Exercise Price Range, lower range limit (in dollars per share) | $ 0.87 | |
Exercise Price Range, upper range limit (in dollars per share) | $ 1.35 | |
Number of outstanding options (in shares) | shares | 4,420,470 | |
Outstanding Options, weighted average remaining contractual term (in years) | 5 years 2 months 12 days | |
Outstanding Options, weighted average exercise price (in dollars per share) | $ 1.19 | |
Number of exercisable options (in shares) | shares | 4,420,470 | |
Exercisable Options, weighted average exercise price (in dollars per share) | $ 1.19 | |
$1.40 - $2.45 | | |
Stock options, additional disclosures [Abstract] | | |
Outstanding Options, weighted average remaining contractual term (in years) | 4 years 4 months 24 days | |
Exercise Price Range, lower range limit (in dollars per share) | $ 1.40 | |
Exercise Price Range, upper range limit (in dollars per share) | $ 2.45 | |
Number of outstanding options (in shares) | shares | 1,458,424 | |
Outstanding Options, weighted average remaining contractual term (in years) | 4 years 4 months 24 days | |
Outstanding Options, weighted average exercise price (in dollars per share) | $ 1.92 | |
Number of exercisable options (in shares) | shares | 1,458,424 | |
Exercisable Options, weighted average exercise price (in dollars per share) | $ 1.92 | |
$2.66 - $3.99 | | |
Stock options, additional disclosures [Abstract] | | |
Outstanding Options, weighted average remaining contractual term (in years) | 6 years 3 months 18 days | |
Exercise Price Range, lower range limit (in dollars per share) | $ 2.66 | |
Exercise Price Range, upper range limit (in dollars per share) | $ 3.99 | |
Number of outstanding options (in shares) | shares | 889,430 | |
Outstanding Options, weighted average remaining contractual term (in years) | 6 years 3 months 18 days | |
Outstanding Options, weighted average exercise price (in dollars per share) | $ 3.06 | |
Number of exercisable options (in shares) | shares | 889,430 | |
Exercisable Options, weighted average exercise price (in dollars per share) | $ 3.06 | |
$4.19 - $6.38 | | |
Stock options, additional disclosures [Abstract] | | |
Outstanding Options, weighted average remaining contractual term (in years) | 6 years 10 months 24 days | |
Exercise Price Range, lower range limit (in dollars per share) | $ 4.19 | |
Exercise Price Range, upper range limit (in dollars per share) | $ 6.38 | |
Number of outstanding options (in shares) | shares | 3,310,253 | |
Outstanding Options, weighted average remaining contractual term (in years) | 6 years 10 months 24 days | |
Outstanding Options, weighted average exercise price (in dollars per share) | $ 5.36 | |
Number of exercisable options (in shares) | shares | 2,898,133 | |
Exercisable Options, weighted average exercise price (in dollars per share) | $ 5.28 | |
$6.45 - $9.78 | | |
Stock options, additional disclosures [Abstract] | | |
Outstanding Options, weighted average remaining contractual term (in years) | 7 years 7 months 6 days | |
Exercise Price Range, lower range limit (in dollars per share) | $ 6.45 | |
Exercise Price Range, upper range limit (in dollars per share) | $ 9.78 | |
Number of outstanding options (in shares) | shares | 2,479,415 | |
Outstanding Options, weighted average remaining contractual term (in years) | 7 years 7 months 6 days | |
Outstanding Options, weighted average exercise price (in dollars per share) | $ 7.29 | |
Number of exercisable options (in shares) | shares | 1,586,502 | |
Exercisable Options, weighted average exercise price (in dollars per share) | $ 7.23 | |
$9.90- $10.99 | | |
Stock options, additional disclosures [Abstract] | | |
Outstanding Options, weighted average remaining contractual term (in years) | 8 years 4 months 24 days | |
Exercise Price Range, lower range limit (in dollars per share) | $ 9.90 | |
Exercise Price Range, upper range limit (in dollars per share) | $ 10.99 | |
Number of outstanding options (in shares) | shares | 107,166 | |
Outstanding Options, weighted average remaining contractual term (in years) | 8 years 4 months 24 days | |
Outstanding Options, weighted average exercise price (in dollars per share) | $ 10.43 | |
Number of exercisable options (in shares) | shares | 36,492 | |
Exercisable Options, weighted average exercise price (in dollars per share) | $ 10.44 | |