FAIR VALUE MEASUREMENT - Fair Value Hierarchy of Financial Instruments Held (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Assets:
U.S. Treasury securities	$ 176.6	$ 70.0
Deferred compensation plan assets	31.0	40.3
Note receivable - building sale	6.4	6.2
Total assets	214.0	116.5
Liabilities:
Deferred compensation plan liabilities	31.0	40.3
Debt	1,345.1	1,317.0
Total liabilities	1,376.1	1,357.3
Level 1
Assets:
U.S. Treasury securities	176.6	70.0
Deferred compensation plan assets	31.0	40.3
Note receivable - building sale	0.0	0.0
Total assets	207.6	110.3
Liabilities:
Deferred compensation plan liabilities	31.0	40.3
Debt	0.0	0.0
Total liabilities	31.0	40.3
Level 2
Assets:
U.S. Treasury securities	0.0	0.0
Deferred compensation plan assets	0.0	0.0
Note receivable - building sale	0.0	0.0
Total assets	0.0	0.0
Liabilities:
Deferred compensation plan liabilities	0.0	0.0
Debt	1,345.1	1,317.0
Total liabilities	1,345.1	1,317.0
Level 3
Assets:
U.S. Treasury securities	0.0	0.0
Deferred compensation plan assets	0.0	0.0
Note receivable - building sale	6.4	6.2
Total assets	6.4	6.2
Liabilities:
Deferred compensation plan liabilities	0.0	0.0
Debt	0.0	0.0
Total liabilities	$ 0.0	$ 0.0