Investments (Impaired Loans) (Details) (USD $) In Millions	9 Months Ended
	Sep. 30, 2011		Dec. 31, 2010
Recorded Investment	$ 562	[1]	$ 1,007	[2]
Unpaid Principal Balance Principal Balance	650		1,028
Related Allowance	155		300
Average Recorded Investment	827	[3]
Interest Income Recognized	11	[4]
Commercial Mortgage Loan [Member] | Impaired Financing Receivable with No Related Allowance [Member]
Recorded Investment	17	[1]	64	[2]
Unpaid Principal Balance Principal Balance	18		64
Related Allowance	0		0
Average Recorded Investment	39	[3]
Interest Income Recognized	1	[4]
Commercial Mortgage Loan [Member] | Impaired Financing Receivable with No Related Allowance [Member] | Commercial Loan On Industrial Properties [Member]
Recorded Investment	0	[1]	0	[2]
Unpaid Principal Balance Principal Balance	0		0
Related Allowance	0		0
Average Recorded Investment	1	[3]
Interest Income Recognized	0	[4]
Commercial Mortgage Loan [Member] | Impaired Financing Receivable with No Related Allowance [Member] | Commercial Loan on Retail [Member]
Recorded Investment	0	[1]	0	[2]
Unpaid Principal Balance Principal Balance	0		0
Related Allowance	0		0
Average Recorded Investment	0	[3]
Interest Income Recognized	0	[4]
Commercial Mortgage Loan [Member] | Impaired Financing Receivable with No Related Allowance [Member] | Commercial Loan on Office [Member]
Recorded Investment	0	[1]	0	[2]
Unpaid Principal Balance Principal Balance	0		0
Related Allowance	0		0
Average Recorded Investment	1	[3]
Interest Income Recognized	0	[4]
Commercial Mortgage Loan [Member] | Impaired Financing Receivable with No Related Allowance [Member] | Commercial Loan On Apartment And Multi Family [Member]
Recorded Investment	0	[1]	0	[2]
Unpaid Principal Balance Principal Balance	0		0
Related Allowance	0		0
Average Recorded Investment	0	[3]
Interest Income Recognized	0	[4]
Commercial Mortgage Loan [Member] | Impaired Financing Receivable with No Related Allowance [Member] | Commercial Loan on Hospitality [Member]
Recorded Investment	0	[1]	64	[2]
Unpaid Principal Balance Principal Balance	0		64
Related Allowance	0		0
Average Recorded Investment	28	[3]
Interest Income Recognized	0	[4]
Commercial Mortgage Loan [Member] | Impaired Financing Receivable with No Related Allowance [Member] | Commercial Loan on Other [Member]
Recorded Investment	17	[1]	0	[2]
Unpaid Principal Balance Principal Balance	18		0
Related Allowance	0		0
Average Recorded Investment	9	[3]
Interest Income Recognized	1	[4]
Uncollateralized Loans [Member] | Impaired Financing Receivable with No Related Allowance [Member]
Recorded Investment	6	[1]	0	[2]
Unpaid Principal Balance Principal Balance	12		12
Related Allowance	0		0
Average Recorded Investment	6	[3]
Interest Income Recognized	0	[4]
Residential Property Loan [Member] | Impaired Financing Receivable with No Related Allowance [Member]
Recorded Investment	0	[1]	0	[2]
Unpaid Principal Balance Principal Balance	0		0
Related Allowance	0		0
Average Recorded Investment	0	[3]
Interest Income Recognized	0	[4]
Other Collateralized Loans [Member] | Impaired Financing Receivable with No Related Allowance [Member]
Recorded Investment	0	[1]	0	[2]
Unpaid Principal Balance Principal Balance	0		0
Related Allowance	0		0
Average Recorded Investment	0	[3]
Interest Income Recognized	0	[4]
Impaired Financing Receivable with No Related Allowance [Member]
Recorded Investment	24	[1]	65	[2]
Unpaid Principal Balance Principal Balance	30		77
Related Allowance	0		0
Average Recorded Investment	46	[3]
Interest Income Recognized	1	[4]
Impaired Financing Receivable with No Related Allowance [Member] | Agricultural Loan [Member]
Recorded Investment	1	[1]	1	[2]
Unpaid Principal Balance Principal Balance	0		1
Related Allowance	0		0
Average Recorded Investment	1	[3]
Interest Income Recognized	0	[4]
Commercial Mortgage Loan [Member] | Impaired Financing Receivable with Related Allowance [Member]
Recorded Investment	481	[1]	852	[2]
Unpaid Principal Balance Principal Balance	563		853
Related Allowance	131		264
Average Recorded Investment	714	[3]
Interest Income Recognized	8	[4]
Commercial Mortgage Loan [Member] | Impaired Financing Receivable with Related Allowance [Member] | Commercial Loan On Industrial Properties [Member]
Recorded Investment	37	[1]	18	[2]
Unpaid Principal Balance Principal Balance	37		18
Related Allowance	19		18
Average Recorded Investment	32	[3]
Interest Income Recognized	0	[4]
Commercial Mortgage Loan [Member] | Impaired Financing Receivable with Related Allowance [Member] | Commercial Loan on Retail [Member]
Recorded Investment	38	[1]	155	[2]
Unpaid Principal Balance Principal Balance	38		155
Related Allowance	4		23
Average Recorded Investment	120	[3]
Interest Income Recognized	1	[4]
Commercial Mortgage Loan [Member] | Impaired Financing Receivable with Related Allowance [Member] | Commercial Loan on Office [Member]
Recorded Investment	58	[1]	43	[2]
Unpaid Principal Balance Principal Balance	140		43
Related Allowance	11		10
Average Recorded Investment	49	[3]
Interest Income Recognized	0	[4]
Commercial Mortgage Loan [Member] | Impaired Financing Receivable with Related Allowance [Member] | Commercial Loan On Apartment And Multi Family [Member]
Recorded Investment	102	[1]	323	[2]
Unpaid Principal Balance Principal Balance	102		323
Related Allowance	19		103
Average Recorded Investment	220	[3]
Interest Income Recognized	3	[4]
Commercial Mortgage Loan [Member] | Impaired Financing Receivable with Related Allowance [Member] | Commercial Loan on Hospitality [Member]
Recorded Investment	151	[1]	218	[2]
Unpaid Principal Balance Principal Balance	151		218
Related Allowance	62		89
Average Recorded Investment	191	[3]
Interest Income Recognized	1	[4]
Commercial Mortgage Loan [Member] | Impaired Financing Receivable with Related Allowance [Member] | Commercial Loan on Other [Member]
Recorded Investment	95	[1]	95	[2]
Unpaid Principal Balance Principal Balance	95		96
Related Allowance	16		21
Average Recorded Investment	102	[3]
Interest Income Recognized	3	[4]
Uncollateralized Loans [Member] | Impaired Financing Receivable with Related Allowance [Member]
Recorded Investment	0	[1]	35	[2]
Unpaid Principal Balance Principal Balance	0		38
Related Allowance	0		16
Average Recorded Investment	15	[3]
Interest Income Recognized	0	[4]
Residential Property Loan [Member] | Impaired Financing Receivable with Related Allowance [Member]
Recorded Investment	0	[1]	26	[2]
Unpaid Principal Balance Principal Balance	0		31
Related Allowance	0		0
Average Recorded Investment	6	[3]
Interest Income Recognized	0	[4]
Other Collateralized Loans [Member] | Impaired Financing Receivable with Related Allowance [Member]
Recorded Investment	39	[1]	29	[2]
Unpaid Principal Balance Principal Balance	39		29
Related Allowance	18		20
Average Recorded Investment	33	[3]
Interest Income Recognized	2	[4]
Impaired Financing Receivable with Related Allowance [Member]
Recorded Investment	538	[1]	942	[2]
Unpaid Principal Balance Principal Balance	620		951
Related Allowance	155		300
Average Recorded Investment	781	[3]
Interest Income Recognized	10	[4]
Impaired Financing Receivable with Related Allowance [Member] | Agricultural Loan [Member]
Recorded Investment	18	[1]	0	[2]
Unpaid Principal Balance Principal Balance	18		0
Related Allowance	6		0
Average Recorded Investment	13	[3]
Interest Income Recognized	0	[4]
Commercial Mortgage Loan [Member]
Recorded Investment	498	[1]	916	[2]
Unpaid Principal Balance Principal Balance	581		917
Related Allowance	131		264
Average Recorded Investment	753	[3]
Interest Income Recognized	9	[4]
Agricultural Loan [Member]
Recorded Investment	19	[1]	1	[2]
Unpaid Principal Balance Principal Balance	18		1
Related Allowance	6		0
Average Recorded Investment	14	[3]
Interest Income Recognized	0	[4]
Residential Property Loan [Member]
Recorded Investment	0	[1]	26	[2]
Unpaid Principal Balance Principal Balance	0		31
Related Allowance	0		0
Average Recorded Investment	6	[3]
Interest Income Recognized	0	[4]
Other Collateralized Loans [Member]
Recorded Investment	39	[1]	29	[2]
Unpaid Principal Balance Principal Balance	39		29
Related Allowance	18		20
Average Recorded Investment	33	[3]
Interest Income Recognized	2	[4]
Uncollateralized Loans [Member]
Recorded Investment	6	[1]	35	[2]
Unpaid Principal Balance Principal Balance	12		50
Related Allowance	0		16
Average Recorded Investment	21	[3]
Interest Income Recognized	$ 0	[4]

[1] Recorded investment reflects the balance sheet carrying value gross of related allowance

[2] Recorded investment reflects the balance sheet carrying value gross of related allowance.

[3] Average recorded investment represents the average of the beginning-of-period and all subsequent quarterly end-of-period balances.

[4] The interest income recognized reflects the related year-to-date income, regardless of the impairment timing.