Summary of Significant Accounting Policies - Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Basic EPS
Net income attributable to common stockholders	$ 40,244	$ 44,662
Weighted-Average Shares (in shares)	10,802,000	10,767,000
Dollars per share (in dollars per share)	$ 3.73	$ 4.15
Effect of dilutive securities
SARs and restricted stock (in shares)	116,000	120,000
SARs and restricted stock (in dollars per share)	$ (0.04)	$ (0.05)
Net income, Diluted EPS	$ 40,244	$ 44,662
Weighted-Average Shares, Diluted EPS (in shares)	10,918,000	10,887,000
Diluted EPS (in dollars per share)	$ 3.69	$ 4.10
Stock Appreciation Rights and Restricted Stock
Effect of dilutive securities
Antidilutive securities excluded from earnings per share (in shares)	62,709	50,005
Performance Shares
Effect of dilutive securities
Antidilutive securities excluded from earnings per share (in shares)	32,282	18,535