Stock Based Compensation - Stock Option Award Activity (Details) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Number of Shares
Outstanding, beginning of year (in shares)	5,399,184	5,974,433	6,094,033
Grants in period, gross	400,000	412,247	486,000
Exercised (in shares)	(1,758,294)	(987,496)	(393,571)
Forfeited (in shares)	0	0	(9,950)
Cancelled (in shares)	0	0	(202,079)
Outstanding, end of year (in shares)	4,040,890	5,399,184	5,974,433
Weighted- Average Exercise Price
Outstanding, beginning of year, weighted average exercise price (in dollars per share)	$ 24.00	$ 23.50	$ 23.35
Granted, Weighted-Average Exercise Price ( in dollars per share)	25.81	35.55	28.45
Exercised, Weighted-Average Exercise Price ( in dollars per share)	21.56	25.65	25.06
Forfeited, Weighted-Average Exercise Price ( in dollars per share)			20.46
Cancelled, Weighted-Average Exercise Price ( in dollars per share)			27.94
Outstanding, end of year, weighted average exercise price (in dollars per share)	$ 25.24	$ 24.00	$ 23.50