Equity, Non-vested Stock Option Activity (Details) - Stock Options - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Status of the Company's non-vested options and changes during the year
Non-vested options at the beginning of the period (in shares)	19,016,830
Non-vested options, options granted (in shares)	6,110,200	6,181,700	6,302,100
Non-vested options, options vested (in shares)	(6,324,610)
Non-vested options, options forfeited (in shares)	(307,770)
Non-vested options at the end of the period (in shares)	18,494,650	19,016,830
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)	$ 10.72
Weighted average fair value at grant date, options granted (in dollars per share)	16.35	$ 12.26	$ 12.82
Weighted average fair value at grant date, options vested (in dollars per share)	9.87
Weighted average fair value at grant date, options forfeited (in dollars per share)	12.03
Weighted average fair value at the grant date, options outstanding at the end of the period (in dollars per share)	$ 12.85	$ 10.72