SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Basic EPS
Net income attributable to common stockholders	$ 46,955	$ 40,244
Net income attributable to common stockholders (in shares)	10,847,000	10,802,000
Net income attributable to common stockholders (in dollars per share)	$ 4.33	$ 3.73
Effect of dilutive securities
SARs and restricted stock units (in shares)	122,000	116,000
SARs and restricted stock units (in dollars per share)	$ (0.05)	$ (0.04)
Net income, diluted EPS	$ 46,955	$ 40,244
Weighted-Average Shares, diluted EPS (in shares)	10,969,000	10,918,000
Diluted EPS (in dollars per share)	$ 4.28	$ 3.69
Stock Appreciation Rights and Restricted Stock
Effect of dilutive securities
Antidilutive securities excluded from earnings per share (in shares)	49,371	62,709
Performance Shares
Effect of dilutive securities
Antidilutive securities excluded from earnings per share (in shares)	29,918	32,282