Stock-Based Compensation, Non-Vested Stock Option Activity (Details) - Stock Options - $ / shares	3 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021
Status of the Company's non-vested options and changes during the year
Non-vested options at the beginning of the period (in shares)	31,905,220	37,082,020	36,989,300
Non-vested options, options granted (in shares)	95,400	7,215,100	215,080
Non-vested options, options vested (in shares)	(134,000)	(12,345,300)	(91,200)
Non-vested options, options forfeited (in shares)	(200,890)	(46,600)	(31,160)
Non-vested options at the end of the period (in shares)	31,665,730	31,905,220	37,082,020
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)	$ 8.30	$ 6.46	$ 6.43
Weighted average fair value at grant date, options granted (in dollars per share)	14.19	13.29	12.11
Weighted average fair value at grant date, options vested (in dollars per share)	4.76	5.70	3.88
Weighted average fair value at grant date, options forfeited (in dollars per share)	8.09	7.97	5.77
Weighted average fair value at the grant date, options outstanding at the end of the period (in dollars per share)	$ 8.33	$ 8.30	$ 6.46