Investments (Details 38) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Financing Receivable, Modifications [Line Items]
Number of Mortgage Loans	0	6	0	9
Pre-Modification		$ 23		$ 85
Post-Modification		23		87
Commercial
Financing Receivable, Modifications [Line Items]
Number of Mortgage Loans	0	1	0	2
Pre-Modification		6		59
Post-Modification		7		60
Agricultural
Financing Receivable, Modifications [Line Items]
Number of Mortgage Loans	0	5	0	7
Pre-Modification		17		26
Post-Modification		$ 16		$ 27