Summary of Significant Accounting Policies - Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Basic EPS
Net income attributable to common stockholders	$ 51,345	$ 34,627	$ 132,010	$ 114,352
Weighted-Average Shares (in shares)	10,839,000	10,799,000	10,825,000	10,787,000
Basic EPS (in dollars per share)	$ 4.74	$ 3.21	$ 12.20	$ 10.61
Effect of dilutive securities
SARs and restricted stock (in shares)	99,000	75,000	99,000	88,000
SARs and restricted stock (in dollars per share)	$ (0.05)	$ (0.03)	$ (0.12)	$ (0.10)
Net income, Diluted EPS	$ 51,345	$ 34,627	$ 132,010	$ 114,352
Weighted-Average Shares, Diluted EPS (in shares)	10,938,000	10,874,000	10,924,000	10,875,000
Diluted EPS (in dollars per share)	$ 4.69	$ 3.18	$ 12.08	$ 10.51
Stock Appreciation Rights and Restricted Stock
Effect of dilutive securities
Antidilutive securities excluded from earnings per share (in shares)	16,761	18,432	37,990	37,120
Performance Shares
Effect of dilutive securities
Antidilutive securities excluded from earnings per share (in shares)	32,469	18,535	32,407	18,535