Supplemental Guarantor/Non-Guarantor Financial Information (Details 3) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2013
Current assets
Cash and cash equivalents	$ 123,519	$ 168,745	$ 119,290	$ 231,633
Accounts receivable	62,029	86,838
Due from related parties	4,152	227
Inventories, net	75,503	79,802
Deferred income taxes	21,670	21,670
Derivative financial instruments	7,258	17,111
Prepaid taxes	9,388	3
Other assets	16,668	9,837
Total current assets	320,187	384,233
Noncurrent assets
Property, plant and equipment, net	1,514,762	1,589,138
Port access contract rights, net	50,997	53,780
Goodwill	2,280	35,634
Deferred income taxes	65,918	56,468
Other assets	44,540	31,900
Total assets	1,998,684	2,151,153
Current liabilities
Accounts payable	54,189	52,035
Royalties and production taxes	126,139	126,212
Accrued expenses	45,989	52,213
Current portion of federal coal lease obligations	0	63,970
Other liabilities	1,803	1,632
Total current liabilities	228,120	296,062
Noncurrent liabilities
Senior notes	490,792	489,715
Asset retirement obligations, net of current portion	167,790	216,241	175,462
Accumulated postretirement medical benefit obligation, net of current portion	55,401	50,276
Other liabilities	12,370	11,025
Total liabilities	$ 954,473	$ 1,063,319
Commitments and Contingencies (Note 13)
Total equity	$ 1,044,211	$ 1,087,834
Total liabilities and equity	1,998,684	2,151,153
Eliminations
Current assets
Cash and cash equivalents	0	0	0	0
Accounts receivable	0	0
Due from related parties	(574,490)	(601,313)
Inventories, net	0	0
Deferred income taxes	(45)	(46)
Derivative financial instruments	0	0
Other assets	0	0
Total current assets	(574,535)	(601,359)
Noncurrent assets
Property, plant and equipment, net	0	0
Port access contract rights, net	0	0
Goodwill	0	0
Deferred income taxes	(8,637)	0
Other assets	(2,946,967)	(3,013,443)
Total assets	(3,530,139)	(3,614,802)
Current liabilities
Accounts payable	0	0
Royalties and production taxes	0	0
Accrued expenses	0	0
Due to related parties	(574,490)	(601,313)
Current portion of federal coal lease obligations	0	0
Other liabilities	(45)	(46)
Total current liabilities	(574,535)	(601,359)
Noncurrent liabilities
Senior notes	0	0
Asset retirement obligations, net of current portion	0	0
Deferred income taxes	(8,637)
Accumulated postretirement medical benefit obligation, net of current portion	0	0
Other liabilities	0	0
Total liabilities	(583,172)	(601,359)
Total equity	(2,946,967)	(3,013,443)
Total liabilities and equity	(3,530,139)	(3,614,802)
Parent Guarantor (CPE Inc.)
Current assets
Cash and cash equivalents	0	0	0	0
Accounts receivable	1	0
Due from related parties	0	0
Inventories, net	0	0
Deferred income taxes	0	0
Derivative financial instruments	0	0
Prepaid taxes	9,388	3
Other assets	577	289
Total current assets	9,966	292
Noncurrent assets
Property, plant and equipment, net	0	0
Port access contract rights, net	0	0
Goodwill	0	0
Deferred income taxes	0	0
Other assets	1,060,437	1,108,101
Total assets	1,070,403	1,108,393
Current liabilities
Accounts payable	212	0
Royalties and production taxes	0	0
Accrued expenses	1,859	6,194
Due to related parties	15,484	14,365
Current portion of federal coal lease obligations	0	0
Other liabilities	0	0
Total current liabilities	17,555	20,559
Noncurrent liabilities
Senior notes	0	0
Asset retirement obligations, net of current portion	0	0
Deferred income taxes	8,637
Accumulated postretirement medical benefit obligation, net of current portion	0	0
Other liabilities	0	0
Total liabilities	$ 26,192	$ 20,559
Commitments and Contingencies (Note 13)
Total equity	$ 1,044,211	$ 1,087,834
Total liabilities and equity	1,070,403	1,108,393
Issuers
Current assets
Cash and cash equivalents	121,055	167,532	118,240	226,993
Accounts receivable	0	0
Due from related parties	0	0
Inventories, net	7,184	6,700
Deferred income taxes	0	0
Derivative financial instruments	0	0
Prepaid taxes	0	0
Other assets	0	6
Total current assets	128,239	174,238
Noncurrent assets
Property, plant and equipment, net	5,280	6,167
Port access contract rights, net	0	0
Goodwill	0	0
Deferred income taxes	48,348	33,926
Other assets	1,890,055	1,910,699
Total assets	2,071,922	2,125,031
Current liabilities
Accounts payable	8,309	1,287
Royalties and production taxes	0	0
Accrued expenses	8,500	5,318
Due to related parties	503,887	520,611
Current portion of federal coal lease obligations	0	0
Other liabilities	45	46
Total current liabilities	520,741	527,262
Noncurrent liabilities
Senior notes	490,792	489,715
Asset retirement obligations, net of current portion	0	0
Deferred income taxes	0
Accumulated postretirement medical benefit obligation, net of current portion	0	0
Other liabilities	0	0
Total liabilities	$ 1,011,533	$ 1,016,978
Commitments and Contingencies (Note 13)
Total equity	$ 1,060,389	$ 1,108,053
Total liabilities and equity	2,071,922	2,125,031
Guarantor Subsidiaries
Current assets
Cash and cash equivalents	2,465	1,213	1,050	496
Accounts receivable	705	14,161
Due from related parties	578,641	601,540
Inventories, net	68,319	73,103
Deferred income taxes	21,715	21,716
Derivative financial instruments	7,258	17,111
Prepaid taxes	0	0
Other assets	16,091	9,541
Total current assets	695,194	738,385
Noncurrent assets
Property, plant and equipment, net	1,509,482	1,582,971
Port access contract rights, net	50,997	53,780
Goodwill	2,280	35,634
Deferred income taxes	26,193	22,542
Other assets	41,015	26,543
Total assets	2,325,161	2,459,855
Current liabilities
Accounts payable	45,653	50,679
Royalties and production taxes	126,139	126,212
Accrued expenses	35,630	40,701
Due to related parties	0	0
Current portion of federal coal lease obligations	0	63,970
Other liabilities	1,803	1,632
Total current liabilities	209,225	283,194
Noncurrent liabilities
Senior notes	0	0
Asset retirement obligations, net of current portion	167,790	216,241
Deferred income taxes	0
Accumulated postretirement medical benefit obligation, net of current portion	55,401	50,276
Other liabilities	12,370	11,025
Total liabilities	$ 444,786	$ 560,736
Commitments and Contingencies (Note 13)
Total equity	$ 1,880,375	$ 1,899,119
Total liabilities and equity	2,325,161	2,459,855
Non-Guarantor Subsidiaries
Current assets
Cash and cash equivalents	0	0	$ 0	$ 4,144
Accounts receivable	61,323	72,676
Due from related parties	0	0
Inventories, net	0	0
Deferred income taxes	0	0
Derivative financial instruments	0	0
Prepaid taxes	0	0
Other assets	0	0
Total current assets	61,323	72,676
Noncurrent assets
Property, plant and equipment, net	0	0
Port access contract rights, net	0	0
Goodwill	0	0
Deferred income taxes	14	0
Other assets	0	0
Total assets	61,337	72,676
Current liabilities
Accounts payable	16	68
Royalties and production taxes	0	0
Accrued expenses	0	0
Due to related parties	55,118	66,337
Current portion of federal coal lease obligations	0	0
Other liabilities	0	0
Total current liabilities	55,134	66,405
Noncurrent liabilities
Senior notes	0	0
Asset retirement obligations, net of current portion	0	0
Deferred income taxes	0
Accumulated postretirement medical benefit obligation, net of current portion	0	0
Other liabilities	0	0
Total liabilities	$ 55,134	$ 66,405
Commitments and Contingencies (Note 13)
Total equity	$ 6,203	$ 6,271
Total liabilities and equity	$ 61,337	$ 72,676