Investments (Details Textuals 16) (USD $)	Sep. 30, 2011	Dec. 31, 2010
Financing Receivable, Modifications [Abstract]
Carrying Value after Specific Valuation Allowance	$ 0
Agricultural mortgage loans portfolio segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Estimated fair value of mortgage loans held-for-investment	13,400,000,000	12,900,000,000
Residential mortgage loans portfolio segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Estimated fair value of mortgage loans held-for-investment	$ 3,500,000,000	$ 2,300,000,000

The amount of the outstanding recorded investment related to financing receivables that have been modified by troubled debt restructurings.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 32

-URI http://asc.fasb.org/extlink&oid=6965416&loc=SL6953670-111524

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 33

-URI http://asc.fasb.org/extlink&oid=6965416&loc=SL6953676-111524

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 40

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6951948&loc=d3e18845-111554

Name:	us-gaap_FinancingReceivableModificationsRecordedInvestment
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant