STOCKHOLDERS' EQUITY - AOCI Components (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Accumulated Other Comprehensive Income
Total after-tax amount	$ 1,242,363	$ 1,151,401	$ 929,067	$ 828,593
Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income
Total pre-tax amount	5,817	9,566	4,977
Total after-tax amount	4,324	7,103	3,699	$ 1,190
Unrecognized Net Periodic Benefit Credit
Accumulated Other Comprehensive Income
Total pre-tax amount	6,816	9,287	5,602
Total after-tax amount	5,061	6,896	4,160
Interest Rate Swap
Accumulated Other Comprehensive Income
Total pre-tax amount	1,710	3,526	419
Total after-tax amount	1,263	2,604	309
Foreign Currency Translation
Accumulated Other Comprehensive Income
Total pre-tax amount	(2,709)	(3,247)	(1,044)
Total after-tax amount	$ (2,000)	$ (2,397)	$ (770)