Equity - Activity of Stock Options (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Number of Shares
Outstanding, beginning of period (in shares)	9,953,575
Granted (in shares)	0	0	0
Exercised (in shares)	(786,708)
Unvested options forfeited (in shares)	0
Vested options expired (in shares)	(5,469,720)
Outstanding, end of period (in shares)	3,697,147	9,953,575
Exercisable, end of period (in shares)	3,697,147
Weighted- Average Exercise Price
Outstanding, weighted average exercise price, beginning of period (in dollars per share)	$ 3.28
Granted, weighted average exercise price (in dollars per share)	0
Exercised, weighted average exercise price (in dollars per share)	4.52
Unvested options forfeited, weighted-average exercise price (in dollars per share)	0
Vested options expired, weighted-average exercise price (in dollars per share)	2.22
Outstanding, weighted average exercise price, end of period (in dollars per share)	4.59	$ 3.28
Exercisable, weighted average exercise price (in dollars per share)	$ 4.59
Stock options, additional disclosures
Outstanding options, weighted average remaining contractual term	3 years 6 months 25 days
Exercisable, weighted average remaining contractual term	3 years 6 months 25 days
Outstanding, aggregate intrinsic value	$ 595,684
Exercisable, aggregate intrinsic value	$ 595,684