Estimated economic life on which depreciation was computed, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 10

-Section S99

-Paragraph 6

-Subparagraph (SX 210.5-04.(c) Schedule III)

-URI http://asc.fasb.org/extlink&oid=6882300&loc=d3e5864-122674

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph c

-Subparagraph Schedule III

-Article 5

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 28

-Article 12

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 970

-SubTopic 360

-Section S99

-Paragraph 1

-Subparagraph (SX 210.12-28)

-URI http://asc.fasb.org/extlink&oid=6590653&loc=d3e638233-123024

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SIGNIFICANT ACCOUNTING POLICIES - Investments and Mortgage Loans (DETAILS) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012 Minimum [Member]	Dec. 31, 2012 Maximum [Member]	Dec. 31, 2012 Commercial Real Estate Portfolio Segment [Member]	Dec. 31, 2011 Commercial Real Estate Portfolio Segment [Member]	Dec. 31, 2012 Agricultural Real Estate Portfolio Segment [Member]	Dec. 31, 2011 Agricultural Real Estate Portfolio Segment [Member]
Mortgage Loans on Real Estate, Write-down or Reserve, Management Judgment Factor [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status			$ 6	$ 7	$ 0	$ 0
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Life Used for Depreciation	40 years 0 months 0 days	50 years 0 months 0 days