Supplemental Guarantor/Non-Guarantor Financial Information (Details 4) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash flows from continuing operations
Net cash provided by (used in) operating activities	$ 57,032	$ 36,330
Investing activities
Purchases of property, plant and equipment	(11,327)	(30,148)
Cash paid for capitalized interest	0	(1,272)
Investment in development projects	(2,110)	(1,500)
Insurance proceeds		2,826
Other	33	46
Net cash provided by (used in) investing activities	(13,404)	(30,048)
Financing activities
Repayment of senior notes	(62,094)	0
Payment of debt refinancing costs	(408)	0
Payments of deferred financing costs		(3,581)
Payment amortized to deferred gain	(6,294)
Proceeds from issuance of common stock	68,850	0
Cash paid for equity offering	(4,490)	0
Other	(1,958)	(1,713)
Net cash provided by (used in) financing activities	(6,394)	(5,294)
Net increase (decrease) in cash and cash equivalents	37,234	988
Cash and cash equivalents at beginning of period	83,708	89,313
Cash and cash equivalents at end of period	120,942	90,301
Parent Guarantor (CPE Inc.) | Reportable Legal Entities [Member]
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
Investment in development projects	0	0
Insurance proceeds		0
Other	0	0
Net cash provided by (used in) investing activities	0	0
Financing activities
Repayment of senior notes	0
Payments of deferred financing costs	0	0
Payment amortized to deferred gain	0
Proceeds from issuance of common stock	0
Cash paid for equity offering	0
Other	0	0
Net cash provided by (used in) financing activities	0	0
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 | Reportable Legal Entities [Member]
Cash flows from continuing operations
Net cash provided by (used in) operating activities	42,610	8,185
Investing activities
Purchases of property, plant and equipment	(1,420)	(1,727)
Investment in development projects	0	0
Insurance proceeds		0
Other	0	0
Net cash provided by (used in) investing activities	(1,420)	(1,727)
Financing activities
Repayment of senior notes	(62,094)
Payments of deferred financing costs	0	(3,581)
Payment amortized to deferred gain	(6,294)
Proceeds from issuance of common stock	68,850
Cash paid for equity offering	(4,490)
Other	(23)	0
Net cash provided by (used in) financing activities	(4,051)	(3,581)
Net increase (decrease) in cash and cash equivalents	37,139	2,877
Cash and cash equivalents at beginning of period	83,673	87,054
Cash and cash equivalents at end of period	120,812	89,931
Guarantor Subsidiaries | Reportable Legal Entities [Member]
Cash flows from continuing operations
Net cash provided by (used in) operating activities	14,014	28,145
Investing activities
Purchases of property, plant and equipment	(9,907)	(28,421)
Cash paid for capitalized interest		(1,272)
Investment in development projects	(2,110)	(1,500)
Insurance proceeds		2,826
Other	33	46
Net cash provided by (used in) investing activities	(11,984)	(28,321)
Financing activities
Repayment of senior notes	0
Payments of deferred financing costs	0	0
Payment amortized to deferred gain	0
Proceeds from issuance of common stock	0
Cash paid for equity offering	0
Other	(1,935)	(1,713)
Net cash provided by (used in) financing activities	(1,935)	(1,713)
Net increase (decrease) in cash and cash equivalents	95	(1,889)
Cash and cash equivalents at beginning of period	35	2,259
Cash and cash equivalents at end of period	130	370
Non-Guarantor Subsidiaries | Reportable Legal Entities [Member]
Cash flows from continuing operations
Net cash provided by (used in) operating activities	408	0
Investing activities
Purchases of property, plant and equipment	0	0
Investment in development projects	0	0
Insurance proceeds		0
Other	0	0
Net cash provided by (used in) investing activities	0	0
Financing activities
Repayment of senior notes	0
Payment of debt refinancing costs	(408)
Payments of deferred financing costs		0
Payment amortized to deferred gain	0
Proceeds from issuance of common stock	0
Cash paid for equity offering	0
Other	0	0
Net cash provided by (used in) financing activities	(408)	0
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