STOCKHOLDERS' EQUITY - AOCI Components (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022
Accumulated Other Comprehensive Income
Total after-tax amount	$ 1,231,538	$ 1,222,733	$ 1,242,363	$ 1,211,361	$ 1,205,859	$ 1,151,401
Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income
Total pre-tax amount	3,315		5,817
Total after-tax amount	2,473	$ 3,345	4,324	6,569	$ 6,386	7,103
Unrecognized Net Periodic Benefit Credit
Accumulated Other Comprehensive Income
Total pre-tax amount	6,315		6,816
Total after-tax amount	4,689		5,061	6,402		6,896
Interest Rate Swap
Accumulated Other Comprehensive Income
Total pre-tax amount	630		1,710
Total after-tax amount	465		1,263	2,183		2,604
Foreign Currency Translation
Accumulated Other Comprehensive Income
Total pre-tax amount	(3,630)		(2,709)
Total after-tax amount	$ (2,681)		$ (2,000)	$ (2,016)		$ (2,397)