Investments (Credit Quality of Agricultural and Residential Mortgage Loans) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Agricultural Mortgage Loans - by Credit Quality Indicator:
Recorded investment in Mortgage Loan	$ 1,310	$ 1,260
% of Total	100.00%	100.00%
Less than 65% [Member]
Agricultural Mortgage Loans - by Credit Quality Indicator:
Recorded investment in Mortgage Loan	1,253	1,184
% of Total	95.60%	94.00%
65% to 75% [Member]
Agricultural Mortgage Loans - by Credit Quality Indicator:
Recorded investment in Mortgage Loan	$ 57	$ 76
% of Total	4.40%	6.00%

Amount before allowance of loans issued to agricultural institutions. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans covered under loss sharing agreements.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=28368275&loc=d3e5066-111524

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 7

-Subparagraph a

-Article 9

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.7(a)(1))

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

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant