UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2022	Jun. 30, 2021
Cash Flows From Operating Activities
Net income (loss)	$ 410.6	$ 290.0	$ (105.0)
Loss from discontinued operations, net of income taxes	0.7	1.5	4.3
Income (loss) from continuing operations, net of income taxes	411.3	291.5	(100.7)
Adjustments to reconcile income (loss) from continuing operations, net of income taxes to net cash provided by (used in) operating activities:
Depreciation, depletion and amortization	73.8	146.7	145.4
Noncash interest expense, net	5.2	9.0	10.8
Deferred income taxes		(1.4)	(0.8)
Noncash share-based compensation		5.4	3.9
Net gain on disposals	(12.8)	(17.7)	(2.4)
Net loss (gain) on early debt extinguishment	2.3	25.8	(15.3)
(Income) loss from equity affiliates	(48.7)	(93.4)	4.4
Foreign currency option contracts		3.0	4.3
Changes in current assets and liabilities:
Accounts receivable		(179.9)	(5.9)
Inventories		(26.2)	29.2
Other current assets		(82.9)	(19.5)
Accounts payable and accrued expenses		(13.1)	(50.2)
Collateral arrangements		(28.2)	(5.3)
Asset retirement obligations		5.2	14.0
Workers’ compensation obligations		(1.6)	0.6
Postretirement benefit obligations		(32.2)	(29.3)
Pension obligations		(1.2)	(1.2)
Other, net		3.3	0.0
Net cash provided by (used in) continuing operations		12.1	(18.0)
Net cash used in discontinued operations		(2.7)	(4.8)
Net cash provided by (used in) operating activities		9.4	(22.8)
Cash Flows From Investing Activities
Additions to property, plant, equipment and mine development		(63.1)	(93.9)
Changes in accrued expenses related to capital expenditures		(9.7)	(4.1)
Proceeds from disposal of assets, net of receivables		23.4	4.9
Contributions to joint ventures		(276.0)	(244.5)
Distributions from joint ventures		280.8	252.6
Advances to related parties		(1.2)	(0.2)
Cash receipts from Middlemount Coal Pty Ltd and other related parties		143.9	2.6
Other, net		(3.6)	0.0
Net cash provided by (used in) investing activities		94.5	(82.6)
Cash Flows From Financing Activities
Proceeds from long-term debt		545.0	0.0
Repayments of long-term debt		(654.8)	(83.1)
Payment of debt issuance and other deferred financing costs		(20.7)	(22.5)
Proceeds from common stock issuances, net of costs		222.0	65.1
Repurchase of employee common stock relinquished for tax withholding		(2.6)	(1.3)
Distributions to noncontrolling interests		(13.8)	(0.1)
Net cash provided by (used in) financing activities		75.1	(41.9)
Net change in cash, cash equivalents and restricted cash		179.0	(147.3)
Cash, cash equivalents and restricted cash at beginning of period		954.3	709.2
Cash, cash equivalents and restricted cash at end of period (1)	1,133.3	1,133.3	$ 561.9
Cash and cash equivalents	1,120.7	1,120.7
Restricted Cash	$ 12.6	$ 12.6