Supplemental Guarantor/Non-Guarantor Financial Information (Details 4) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Cash flows from continuing operations
Net cash provided by (used in) operating activities	$ 14,887	$ 35,381
Investing activities
Purchases of property, plant and equipment	(14,782)	(7,146)
Investments in marketable securities	0	(8,159)
Maturity and redemption of investments	0	88,845
Investment in development projects	(1,500)	(1,500)
Payment of restricted cash	(6,500)	0
Other	(184)	222
Net cash provided by (used in) investing activities	(22,966)	72,262
Financing activities
Principal payments on federal coal leases	(63,970)	0
Issuance of senior notes	0	200,000
Repayment of senior notes	0	(300,000)
Payment of deferred financing costs	(341)	(13,598)
Other	(817)	(194)
Net cash provided by (used in) financing activities	(65,128)	(113,792)
Net increase (decrease) in cash and cash equivalents	(73,207)	(6,149)
Cash and cash equivalents at beginning of period	168,745	231,633
Cash and cash equivalents at end of period	95,538	225,484
Eliminations
Cash flows from continuing operations
Net cash provided by (used in) operating activities	0	0
Investing activities
Purchases of property, plant and equipment	0	0
Investments in marketable securities	0	0
Maturity and redemption of investments	0	0
Investment in development projects	0	0
Payment of restricted cash	0	0
Contributions made to subsidiary		1,000
Other	0	0
Net cash provided by (used in) investing activities	0	1,000
Financing activities
Issuance of senior notes	0	0
Repayment of senior notes	0	0
Payment of deferred financing costs	0	0
Contributions received from parent		(1,000)
Other	0	0
Net cash provided by (used in) financing activities	0	(1,000)
Net increase (decrease) in cash and cash equivalents	0	0
Cash and cash equivalents at beginning of period	0	0
Cash and cash equivalents at end of period	0	0
Parent Guarantor (CPE Inc.)
Cash flows from continuing operations
Net cash provided by (used in) operating activities	0	(594)
Investing activities
Purchases of property, plant and equipment	0	0
Investments in marketable securities	0	0
Maturity and redemption of investments	0	0
Investment in development projects	0	0
Payment of restricted cash	0	0
Contributions made to subsidiary		0
Other	0	0
Net cash provided by (used in) investing activities	0	0
Financing activities
Principal payments on federal coal leases	0
Issuance of senior notes	0	0
Repayment of senior notes	0	0
Payment of deferred financing costs	0	0
Contributions received from parent		0
Other	0	594
Net cash provided by (used in) financing activities	0	594
Net increase (decrease) in cash and cash equivalents	0	0
Cash and cash equivalents at beginning of period	0	0
Cash and cash equivalents at end of period	0	0
Issuers
Cash flows from continuing operations
Net cash provided by (used in) operating activities	(71,307)	29,347
Investing activities
Purchases of property, plant and equipment	(2,123)	(1,165)
Investments in marketable securities	0	(8,159)
Maturity and redemption of investments	0	88,845
Investment in development projects	0	0
Payment of restricted cash	0	0
Contributions made to subsidiary		0
Other	0	0
Net cash provided by (used in) investing activities	(2,123)	79,521
Financing activities
Principal payments on federal coal leases	0
Issuance of senior notes	0	200,000
Repayment of senior notes	0	(300,000)
Payment of deferred financing costs	(2)	(13,598)
Contributions received from parent		0
Other	0	0
Net cash provided by (used in) financing activities	(2)	(113,598)
Net increase (decrease) in cash and cash equivalents	(73,432)	(4,730)
Cash and cash equivalents at beginning of period	167,532	226,993
Cash and cash equivalents at end of period	94,100	222,263
Guarantor Subsidiaries
Cash flows from continuing operations
Net cash provided by (used in) operating activities	86,194	10,432
Investing activities
Purchases of property, plant and equipment	(12,659)	(5,981)
Investments in marketable securities	0	0
Maturity and redemption of investments	0	0
Investment in development projects	(1,500)	(1,500)
Payment of restricted cash	(6,500)	0
Contributions made to subsidiary		(1,000)
Other	(184)	222
Net cash provided by (used in) investing activities	(20,843)	(8,259)
Financing activities
Principal payments on federal coal leases	(63,970)
Issuance of senior notes	0	0
Repayment of senior notes	0	0
Payment of deferred financing costs	(339)	0
Contributions received from parent		0
Other	(817)	(788)
Net cash provided by (used in) financing activities	(65,126)	(788)
Net increase (decrease) in cash and cash equivalents	225	1,385
Cash and cash equivalents at beginning of period	1,213	496
Cash and cash equivalents at end of period	1,438	1,881
Non-Guarantor Subsidiaries
Cash flows from continuing operations
Net cash provided by (used in) operating activities	0	(3,804)
Investing activities
Purchases of property, plant and equipment	0	0
Investments in marketable securities	0	0
Maturity and redemption of investments	0	0
Investment in development projects	0	0
Payment of restricted cash	0	0
Contributions made to subsidiary		0
Other	0	0
Net cash provided by (used in) investing activities	0	0
Financing activities
Principal payments on federal coal leases	0
Issuance of senior notes	0	0
Repayment of senior notes	0	0
Payment of deferred financing costs	0	0
Contributions received from parent		1,000
Other	0	0
Net cash provided by (used in) financing activities	0	1,000
Net increase (decrease) in cash and cash equivalents	0	(2,804)
Cash and cash equivalents at beginning of period	0	4,144
Cash and cash equivalents at end of period	$ 0	$ 1,340