UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Cash Flows From Operating Activities
Net income	$ 202.8	$ 410.6	$ 485.6	$ 290.0
Loss from discontinued operations, net of income taxes	1.3	0.7	2.6	1.5
Income from continuing operations, net of income taxes	204.1	411.3	488.2	291.5
Adjustments to reconcile income from continuing operations, net of income taxes to net cash provided by operating activities:
Depreciation, depletion and amortization	80.6	73.8	156.9	146.7
Noncash interest expense, net			3.3	9.0
Deferred income taxes			65.0	(1.4)
Noncash share-based compensation			3.4	5.4
Asset impairment	0.0	0.0	2.0	0.0
Net gain on disposals	(5.2)	(12.8)	(7.1)	(17.7)
Noncash income from port and rail capacity assignment	(9.3)	0.0	(9.2)
Net loss on early debt extinguishment	2.0	2.3	8.8	25.8
Income from equity affiliates	(2.3)	(48.7)	(4.1)	(93.4)
Foreign currency option contracts			(0.6)	3.0
Changes in current assets and liabilities:
Accounts receivable			149.3	(179.9)
Inventories			(20.8)	(26.2)
Other current assets			43.4	(82.9)
Accounts payable and accrued expenses			(23.3)	(13.1)
Collateral arrangements			(116.9)	(28.2)
Asset retirement obligations			3.6	5.2
Workers’ compensation obligations			(0.7)	(1.6)
Postretirement benefit obligations			(30.4)	(32.2)
Pension obligations			0.7	(1.2)
Other, net			0.0	3.3
Net cash provided by continuing operations			745.2	12.1
Net cash used in discontinued operations			(5.5)	(2.7)
Net cash provided by operating activities			739.7	9.4
Cash Flows From Investing Activities
Additions to property, plant, equipment and mine development			(122.3)	(63.1)
Changes in accrued expenses related to capital expenditures			(5.4)	(9.7)
Proceeds from disposal of assets, net of receivables			12.0	23.4
Contributions to joint ventures			(370.8)	(276.0)
Distributions from joint ventures			365.8	280.8
Advances to related parties			(0.1)	(1.2)
Cash receipts from Middlemount Coal Pty Ltd and other related parties			1.7	143.9
Other, net			(0.9)	(3.6)
Net cash (used in) provided by investing activities			(120.0)	94.5
Cash Flows From Financing Activities
Proceeds from long-term debt			0.0	545.0
Repayments of long-term debt			(4.8)	(654.8)
Payment of debt issuance and other deferred financing costs			(0.3)	(20.7)
Proceeds from Issuance of Common Stock			0.0	222.0
Common stock repurchases			(173.0)	0.0
Repurchase of employee common stock relinquished for tax withholding			(13.7)	(2.6)
Dividends paid			(10.8)	0.0
Distributions to noncontrolling interests			(22.8)	(13.8)
Net cash (used in) provided by financing activities			(225.4)	75.1
Net change in cash, cash equivalents and restricted cash			394.3	179.0
Cash, cash equivalents and restricted cash at beginning of period (1)			1,417.6	954.3
Cash, cash equivalents and restricted cash at end of period (2)	1,811.9	1,133.3	1,811.9	1,133.3
Cash and cash equivalents	1,080.5		1,080.5
Restricted Cash	731.4		731.4
Provision for NARM and Shoal Creek loss	$ 33.7	$ 0.0	$ 33.7	$ 0.0