Stock-Based Compensation, Non-Vested Stock Option Activity (Details) - Stock Options - $ / shares	3 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019
Status of the Company's non-vested options and changes during the year
Non-vested options at the beginning of the period (in shares)	19,216,100	19,227,160	19,289,500
Options granted (in shares)	31,000	6,105,700	40,000
Non-vested options, options vested (in shares)	(100,420)	(6,061,740)	(61,900)
Non-vested options, options forfeited (in shares)	(70,910)	(55,020)	(40,440)
Non-vested options at the end of the period (in shares)	19,075,770	19,216,100	19,227,160
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)	$ 10.71	$ 9.74	$ 9.73
Weighted average fair value at grant date, options granted (in dollars per share)	12.85	12.27	10.48
Weighted average fair value at grant date, options vested (in dollars per share)	8.78	9.19	8.27
Weighted average fair value at grant date, options forfeited (in dollars per share)	10.58	10.87	9.74
Weighted average fair value at the grant date, options outstanding at the end of the period (in dollars per share)	$ 10.72	$ 10.71	$ 9.74