STOCKHOLDERS' EQUITY - AOCI Components (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022
Accumulated Other Comprehensive Income
Total after-tax amount	$ 1,222,733	$ 1,242,363	$ 1,205,859	$ 1,151,401
Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income
Total pre-tax amount	4,493	5,817
Total after-tax amount	3,345	4,324	6,386	7,103
Unrecognized Net Periodic Benefit Credit
Accumulated Other Comprehensive Income
Total pre-tax amount	6,564	6,816
Total after-tax amount	4,874	5,061	6,649	6,896
Interest Rate Swap
Accumulated Other Comprehensive Income
Total pre-tax amount	1,214	1,710
Total after-tax amount	897	1,263	2,152	2,604
Foreign Currency Translation
Accumulated Other Comprehensive Income
Total pre-tax amount	(3,285)	(2,709)
Total after-tax amount	$ (2,426)	$ (2,000)	$ (2,415)	$ (2,397)