Condensed Consolidated Statements Of Cash Flows - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
OPERATING ACTIVITIES
Net income	$ 150.8	$ 75.0	$ 176.3
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation expense		68.6	56.5
Accretion of discount on the Notes Receivable from ARO		(12.3)	(27.6)
Share-based compensation expense		11.6	15.4
Equity in earnings of ARO	0.3	(1.5)	(2.1)
Deferred income tax expense	13.5	173.3	15.5
Net (gain) loss on sale of property		(27.9)	0.1
Loss on impairment	0.0	7.8	0.0
Changes in contract liabilities		(33.4)	(24.8)
Changes in deferred costs		4.3	(0.8)
Other		4.4	4.2
Changes in operating assets and liabilities		14.3	(168.8)
Contributions to pension plans and other post-retirement benefits		(8.3)	(6.1)
Net cash provided by operating activities		275.9	37.8
INVESTING ACTIVITIES
Additions to property and equipment		(167.4)	(261.5)
Proceeds from disposition of assets		27.6	0.1
Net cash used in investing activities		(139.8)	(261.4)
FINANCING ACTIVITIES
Other		(0.4)	(1.8)
Net cash used in financing activities		(0.4)	(1.8)
INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS AND RESTRICTED CASH		135.7	(225.4)
CASH AND CASH EQUIVALENTS AND RESTRICTED CASH, BEGINNING OF PERIOD		380.5	635.7
CASH AND CASH EQUIVALENTS AND RESTRICTED CASH, END OF PERIOD	$ 410.3	$ 516.2	$ 410.3