Equity - Activity of Stock Options (Details)	12 Months Ended
	Dec. 31, 2016 USD ($) $ / shares shares
Number of Shares
Outstanding, beginning of period (in shares) | shares	14,019,629
Granted (in shares) | shares	0
Exercised (in shares) | shares	(1,164,138)
Unvested options forfeited (in shares) | shares	(154,200)
Vested options expired (in shares) | shares	(148,683)
Outstanding, end of period (in shares) | shares	12,552,608
Vested at end of period (in shares) | shares	11,680,455
Vested and expected to vest (in shares) | shares	12,539,865
Weighted- Average Exercise Price
Outstanding, weighted average exercise price, beginning of period (in dollars per share) | $ / shares	$ 3.62
Granted, weighted average exercise price (in dollars per share) | $ / shares	0.00
Exercised, weighted average exercise price (in dollars per share) | $ / shares	3.02
Unvested options forfeited, weighted-average exercise price (in dollars per share) | $ / shares	6.77
Vested options expired, weighted-average exercise price (in dollars per share) | $ / shares	6.16
Outstanding, weighted average exercise price, end of period (in dollars per share) | $ / shares	3.61
Vested at end of period, weighted average exercise price (in dollars per share) | $ / shares	3.33
Vested and expected to vest, weighted average exercise price (in dollars per share) | $ / shares	$ 3.60
Stock options, additional disclosures
Outstanding options, weighted average remaining contractual term	5 years 4 months 24 days
Vested at end of period weighted average remaining contractual term	5 years 3 months 18 days
Vested and expected to vest, weighted average remaining contractual term	5 years 4 months 24 days
Outstanding, aggregate intrinsic value | $	$ 66,137,378
Vested at end of period, aggregate intrinsic value | $	64,733,964
Vested and expected to vest, aggregate intrinsic value | $	$ 66,119,285