Earnings Per Share Summary of Computation of Basic and Diluted Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Net Income (Loss) Available to Common Stockholders, Basic									$ 127,923	$ 102,700	$ 110,387
Weighted Average Number of Shares Outstanding, Basic	16,310,551,000	16,300,720,000	16,296,427,000	16,303,602,000	16,342,485,000	16,382,798,000	16,560,545,000	15,651,541,000	16,302,825	16,234,342	15,488,982
Weighted Average Number Diluted Shares Outstanding Adjustment									104,677	95,114	122,507
Weighted Average Number of Shares Outstanding, Diluted	16,434,812,000	16,393,792,000	16,375,434,000	16,425,881,000	16,454,553,000	16,475,741,000	16,642,571,000	15,744,777,000	16,407,502	16,329,456	15,611,489
Basic (in dollars per share)	$ 2.77	$ 1.89	$ 1.81	$ 1.37	$ 1.46	$ 1.90	$ 1.34	$ 1.63	$ 7.85	$ 6.33	$ 7.13
Diluted (in dollars per share)	$ 2.75	$ 1.88	$ 1.80	$ 1.36	$ 1.45	$ 1.89	$ 1.33	$ 1.62	$ 7.80	$ 6.29	$ 7.07