STOCKHOLDERS' EQUITY - AOCI (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2022	Dec. 31, 2021
Accumulated Other Comprehensive Income
Total after-tax amount	$ 1,205,859	$ 1,151,401	$ 983,172	$ 929,067
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income
Total pre-tax amount	8,596	9,566
Total after-tax amount	6,386	7,103	5,323	3,699
Unrecognized Net Periodic Benefit Credit
Accumulated Other Comprehensive Income
Total pre-tax amount	8,954	9,287
Total after-tax amount	6,649	6,896	4,019	4,160
Interest Rate Swap
Accumulated Other Comprehensive Income
Total pre-tax amount	2,913	3,526
Total after-tax amount	2,152	2,604	1,767	309
Foreign Currency Translation
Accumulated Other Comprehensive Income
Total pre-tax amount	(3,271)	(3,247)
Total after-tax amount	$ (2,415)	$ (2,397)	$ (463)	$ (770)