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Quarterly Financial Data Unaudited (Details Textual) (USD $) | 3 Months Ended | 12 Months Ended
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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)

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- Definition The sum of domestic current and deferred income tax expense or benefit attributable to continuing operations. + References 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 + Details
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