Equity, Unvested Stock Option Activity (Details) - Stock Options - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Status of the Company's non-vested options and changes during the year
Non-vested options at the beginning of the period (in shares)	19,600,440
Options granted (in shares)	6,302,100	7,029,600	7,560,450
Non-vested options, options vested (in shares)	(6,104,120)
Non-vested options, options forfeited (in shares)	(508,920)
Non-vested options at the end of the period (in shares)	19,289,500	19,600,440
Weighted Average Fair Value at Grant Date
Weighted average fair value at the grant date, options outstanding at the beginning of the period (in dollars per share)	$ 8.29
Weighted average fair value at grant date, options granted (in dollars per share)	12.82	$ 8.78	$ 7.39
Weighted average fair value at grant date, options vested (in dollars per share)	8.35
Weighted average fair value at grant date, options forfeited (in dollars per share)	9.09
Weighted average fair value at the grant date, options outstanding at the end of the period (in dollars per share)	$ 9.73	$ 8.29