Summary of Significant Accounting Policies - Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Earnings Per Share, Basic [Abstract]
Net income attributable to common stockholders	$ 41,046	$ 27,958
Weighted-Average Shares (in shares)	10,767,000	10,738,000
Dollars per share (in dollars per share)	$ 3.81	$ 2.60
Effect of dilutive securities
SARs and restricted stock (in shares)	120,000	81,000
SARs and restricted stock (in dollars per share)	$ (0.04)	$ (0.02)
Net income, Diluted EPS	$ 41,046	$ 27,958
Weighted-Average Shares, Diluted EPS (in shares)	10,887,000	10,819,000
Diluted EPS (in dollars per share)	$ 3.77	$ 2.58
Stock Appreciation Rights and Restricted Stock
Effect of dilutive securities
Antidilutive securities excluded from earnings per share (in shares)	50,005	99,684
Performance Shares
Effect of dilutive securities
Antidilutive securities excluded from earnings per share (in shares)	18,535	18,183