SUPPLEMENTAL CASH FLOW INFORMATION - SUPPLEMENTAL INFORMATION (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2025	Mar. 31, 2024
Supplemental cash flow information
Cash paid for interest, net of amount capitalized	$ 132.4	$ 158.6
Cash received for income taxes, net	0.0	(83.0)
Cash received from sale of production tax credits		83.4
Significant non-cash investing and financing transactions
Accounts payable related to construction costs	146.7	147.2
Common stock issued for stock-based compensation plans	3.2	6.2
Increase in receivable for corporate-owned life insurance proceeds	$ 4.0	$ 0.0

Future cash outflow to pay for purchases of fixed assets that have occurred.

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Amount, after refund, of cash paid to foreign, federal, state, and local jurisdictions as income tax.

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