Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash Flows From Operating Activities
Net loss	$ (1,988.9)	$ (777.3)	$ (512.6)
Loss from discontinued operations, net of income taxes	175.0	28.2	226.6
Loss from continuing operations, net of income taxes	(1,813.9)	(749.1)	(286.0)
Adjustments to reconcile loss from continuing operations, net of income taxes to net cash (used in) provided by operating activities:
Depreciation, depletion and amortization	572.2	655.7	740.3
Noncash interest expense	30.6	23.6	32.0
Deferred income taxes	(107.6)	231.9	(434.1)
Share-based Compensation, Total	28.2	46.8	50.9
Asset impairment	1,277.8	154.4	528.3
Settlement charges related to the Patriot bankruptcy	0.0	0.0	30.6
Net gain on disposal of assets	(45.0)	(41.4)	(52.6)
Loss from equity affiliates	15.9	107.6	40.2
Gains on previously monetized foreign currency hedge positions	(14.9)	(136.9)	0.0
Changes in current assets and liabilities:
Accounts receivable	188.0	55.4	104.8
Change in receivable from accounts receivable securitization program	138.5	(70.0)	75.0
Inventories	96.2	104.9	39.9
Net assets from coal trading activities	(27.3)	(10.1)	(83.7)
Other current assets	14.8	7.7	3.1
Accounts payable and accrued expenses	(381.7)	(29.2)	(108.9)
Asset retirement obligations	23.9	60.3	45.5
Workers' compensation obligations	(4.2)	2.2	7.3
Accrued postretirement benefit costs	18.7	9.6	17.0
Accrued pension costs	29.6	28.3	51.8
Other, net	(20.9)	(10.7)	(21.3)
Net cash provided by continuing operations	18.9	441.0	780.1
Net cash used in discontinued operations	(33.3)	(104.4)	(57.7)
Net cash provided by operating activities	(14.4)	336.6	722.4
Cash Flows From Investing Activities
Additions to property, plant, equipment and mine development	(126.8)	(194.4)	(328.4)
Changes in accrued expenses related to capital expenditures	(9.2)	(16.6)	(120.7)
Federal coal lease expenditures	(277.2)	(276.7)	(276.8)
Proceeds from disposal of assets, net of notes receivable	70.4	203.7	178.3
Purchases of debt and equity securities	(28.8)	(15.1)	(22.8)
Proceeds from sales and maturities of debt and equity securities	90.3	13.5	22.9
Maturity of short-term investments	0.0	0.0	4.8
Contributions to joint ventures	(425.4)	(529.8)	(671.7)
Distributions from joint ventures	422.6	534.2	722.9
Advances to related parties	(3.7)	(33.7)	(42.1)
Repayment of loans from related parties	0.9	5.4	25.2
Other, net	(3.1)	(5.0)	(5.8)
Net cash used in continuing operations	(290.0)	(314.5)	(514.2)
Net cash used in discontinued operations	0.0	0.0	(1.5)
Net cash used in investing activities	(290.0)	(314.5)	(515.7)
Cash Flows From Financing Activities
Proceeds from long-term debt	975.7	1.1	1,188.0
Repayments of long-term debt	(671.3)	(21.0)	(1,390.2)
Payment of deferred financing costs	(28.7)	(10.1)	(22.8)
Dividends paid	(1.4)	(92.3)	(91.7)
Restricted cash for distributions to noncontrolling interests	0.0	(42.5)	0.0
Other, net	(6.6)	(3.3)	(4.8)
Net cash used in financing activities	267.7	(168.1)	(321.5)
Net change in cash and cash equivalents	(36.7)	(146.0)	(114.8)
Cash and cash equivalents at beginning of year	298.0	444.0	558.8
Cash and cash equivalents at end of year	$ 261.3	$ 298.0	$ 444.0