Fair Value Measurement (Details Textuals) (USD $)	Jun. 30, 2013	Dec. 31, 2012
Unsecured Debt [Member] \| Twenty Eighteen [Member] \| Eight Point Eight Seven Five Percent [Member]
Debt Instrument [Line Items]
Senior Notes	$ 716,300,000	$ 715,300,000
Debt Instrument, Interest Rate, Stated Percentage	8.875%
Unsecured Debt [Member] \| Twenty Twentytwo [Member] \| Seven Point One Two Five Percent [Member]
Debt Instrument [Line Items]
Senior Notes	250,000,000.0
Debt Instrument, Interest Rate, Stated Percentage	7.125%
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Borrowed under existing credit facility	0	71,000,000
CEI Credit Facility [Member]
Debt Instrument [Line Items]
Borrowed under existing credit facility	$ 26,400,000

Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.16)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 9

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.16(a))

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Name:	us-gaap_SeniorNotes
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant