Segment Information (Schedule Of Operating Segment Results) (Details) $ in Thousands	3 Months Ended
Mar. 31, 2017 USD ($) Segment	Mar. 31, 2016 USD ($)
Segment Reporting [Abstract]
Number of reportable segments \| Segment	2
Successor [Member]
Segment Reporting Information [Line Items]
Revenues	$ 600,975
Adjusted EBITDAR	120,498
Depreciation, depletion and amortization	31,921
Accretion on asset retirement obligations	7,623
Capital expenditures	5,950
Successor [Member] \| Operating Segments [Member] \| PRB [Member]
Segment Reporting Information [Line Items]
Revenues	273,428
Adjusted EBITDAR	48,006
Depreciation, depletion and amortization	9,510
Accretion on asset retirement obligations	5,040
Capital expenditures	128
Successor [Member] \| Operating Segments [Member] \| MET [Member]
Segment Reporting Information [Line Items]
Revenues	225,582
Adjusted EBITDAR	68,310
Depreciation, depletion and amortization	18,764
Accretion on asset retirement obligations	528
Capital expenditures	4,610
Successor [Member] \| Operating Segments [Member] \| Other Thermal [Member]
Segment Reporting Information [Line Items]
Revenues	101,906
Adjusted EBITDAR	27,242
Depreciation, depletion and amortization	3,200
Accretion on asset retirement obligations	540
Capital expenditures	741
Successor [Member] \| Corporate, Other and Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	59
Adjusted EBITDAR	(23,060)
Depreciation, depletion and amortization	447
Accretion on asset retirement obligations	1,515
Capital expenditures	$ 471
Predecessor [Member]
Segment Reporting Information [Line Items]
Revenues		$ 428,106
Adjusted EBITDAR		(1,720)
Depreciation, depletion and amortization		63,699
Accretion on asset retirement obligations		8,306
Capital expenditures		5,926
Predecessor [Member] \| Operating Segments [Member] \| PRB [Member]
Segment Reporting Information [Line Items]
Revenues		223,122
Adjusted EBITDAR		12,728
Depreciation, depletion and amortization		32,760
Accretion on asset retirement obligations		5,647
Capital expenditures		10
Predecessor [Member] \| Operating Segments [Member] \| MET [Member]
Segment Reporting Information [Line Items]
Revenues		136,583
Adjusted EBITDAR		6,352
Depreciation, depletion and amortization		19,345
Accretion on asset retirement obligations		588
Capital expenditures		3,604
Predecessor [Member] \| Operating Segments [Member] \| Other Thermal [Member]
Segment Reporting Information [Line Items]
Revenues		56,132
Adjusted EBITDAR		3,151
Depreciation, depletion and amortization		9,891
Accretion on asset retirement obligations		663
Capital expenditures		1,945
Predecessor [Member] \| Corporate, Other and Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues		12,269
Adjusted EBITDAR		(23,951)
Depreciation, depletion and amortization		1,703
Accretion on asset retirement obligations		1,408
Capital expenditures		$ 367

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Amount of accretion expense recognized during the period that is associated with an asset retirement obligation. Accretion expense measures and incorporates changes due to the passage of time into the carrying amount of the liability.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)(3)
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
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Revenue derived from sale of coal and related products. Also includes rendering of services and selling of products for exploration, development, mining, and processing, as well as supporting activities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
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The cash outflow associated with the acquisition of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale; includes cash outflows to pay for construction of self-constructed assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Investing Activities
-URI http://asc.fasb.org/extlink&oid=6516133

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