Earnings Per Share - Summary of 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]
Basic weighted average number of shares outstanding										12,642,576	12,904,397	13,248,876
Net dilutive effect of share-based awards, treasury method	[1]									574,759	947,435	812,493
Diluted weighted average number of shares outstanding										13,217,335	13,851,832	14,061,369
Net income		$ 81,880	$ 15,639	$ 17,649	$ 7,818	$ 25,435	$ 3,949	$ 12,375	$ 11,194	$ 122,986	$ 52,953	$ 28,892
Diluted earnings per share		$ 6.17	$ 1.19	$ 1.34	$ 0.58	$ 1.83	$ 0.29	$ 0.89	$ 0.81	$ 9.30	$ 3.82	$ 2.05
Earnings Per Share, Basic		$ 6.56	$ 1.25	$ 1.40	$ 0.61	$ 1.99	$ 0.31	$ 0.95	$ 0.86	$ 9.73	$ 4.10	$ 2.18

[1] For the year ended December 31, 2020, the diluted net income per share computation does not include the anti-dilutive effect of 10,770 shares of Class A Stock granted under share-based compensation arrangements (7,628 and 4,050 shares for the years ended December 31, 2019 and 2018, respectively).