Investments (Commercial Mortgage And Other Loans Sold And Acquired) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011
Commercial Mortgage And Other Loans Sold and Acquired [Line Items]
Acquired	$ 838	[1]
Sold	183	[2]
Commercial Mortgage Loan [Member]
Commercial Mortgage And Other Loans Sold and Acquired [Line Items]
Acquired	52	[1]
Sold	147	[2]
Agricultural Property Loans [Member]
Commercial Mortgage And Other Loans Sold and Acquired [Line Items]
Acquired	0	[1]
Sold	0	[2]
Residential Property Loans [Member]
Commercial Mortgage And Other Loans Sold and Acquired [Line Items]
Acquired	219	[1]
Sold	0	[2]
Other Collateralized Loans [Member]
Commercial Mortgage And Other Loans Sold and Acquired [Line Items]
Acquired	2	[1]
Sold	11	[2]
Uncollateralized Loans [Member]
Commercial Mortgage And Other Loans Sold and Acquired [Line Items]
Acquired	565	[1]
Sold	$ 25	[2]

[1] Reported at purchase price of commercial mortgage and other loans acquired.

[2] Reported at book value of commercial mortgage and other loans sold.