Quarterly Financial Data Unaudited (Details Textual) (USD $)	3 Months Ended	12 Months Ended
Dec. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Quarterly Financial Data (Unaudited) (Textual) [Abstract]
Federal income tax expense (benefit)	$ 27,400,000	$ 5,636,000	$ (27,361,000)	$ (47,000)

The sum of domestic current and deferred income tax expense or benefit attributable to continuing operations.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 08

-Paragraph h

-Subparagraph 1

-Article 4

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 10

-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32672-109319

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Income Tax Expense (or Benefit)

-URI http://asc.fasb.org/extlink&oid=6515339

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(h)(1))

-URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690

Name:	us-gaap_FederalIncomeTaxExpenseBenefitContinuingOperations
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration