Investments (Impaired Loans) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011
Recorded Investment	$ 246	[1]	$ 578	[2]
Unpaid Principal Balance Principal Balance	387		667
Related Allowance	73		149
Average Recorded Investment	444	[3]	779	[4]
Interest Income Recognized	12	[5]	13	[6]
Commercial Mortgage Loan [Member]
Recorded Investment	212	[1],[7]	532	[2],[8]
Unpaid Principal Balance Principal Balance	351	[7]	614	[8]
Related Allowance	50	[7]	120	[8]
Average Recorded Investment	405	[3],[7]	709	[4],[8]
Interest Income Recognized	12	[5],[7]	11	[6],[8]
Agricultural Loan [Member]
Recorded Investment	17	[1]	19	[2]
Unpaid Principal Balance Principal Balance	17		19
Related Allowance	12		11
Average Recorded Investment	16	[3]	15	[4]
Interest Income Recognized	0	[5]	0	[6]
Residential Property Loan [Member]
Recorded Investment	0	[1]	0	[2]
Unpaid Principal Balance Principal Balance	0		0
Related Allowance	0		0
Average Recorded Investment	0	[3]	5	[4]
Interest Income Recognized	0	[5]	0	[6]
Other Collateralized Loans [Member]
Recorded Investment	17	[1]	21	[2]
Unpaid Principal Balance Principal Balance	17		21
Related Allowance	11		18
Average Recorded Investment	19	[3]	31	[4]
Interest Income Recognized	0	[5]	2	[6]
Uncollateralized Loans [Member]
Recorded Investment	0	[1]	6	[2]
Unpaid Principal Balance Principal Balance	2		13
Related Allowance	0		0
Average Recorded Investment	4	[3]	19	[4]
Interest Income Recognized	0	[5]	0	[6]
Impaired Mortgage with No Related Allowance [Member]`
Recorded Investment	27	[1]	25	[2]
Unpaid Principal Balance Principal Balance	168		114
Related Allowance	0		0
Average Recorded Investment	58	[3]	42	[4]
Interest Income Recognized	4	[5]	1	[6]
Impaired Mortgage with No Related Allowance [Member]` | Commercial Mortgage Loan [Member]
Recorded Investment	27	[1],[7]	19	[2],[8]
Unpaid Principal Balance Principal Balance	166	[7]	101	[8]
Related Allowance	0	[7]	0	[8]
Average Recorded Investment	54	[3],[7]	35	[4],[8]
Interest Income Recognized	4	[5],[7]	1	[6],[8]
Impaired Mortgage with No Related Allowance [Member]` | Agricultural Loan [Member]
Recorded Investment	0	[1]	0	[2]
Unpaid Principal Balance Principal Balance	0		0
Related Allowance	0		0
Average Recorded Investment	0	[3]	1	[4]
Interest Income Recognized	0	[5]	0	[6]
Impaired Mortgage with No Related Allowance [Member]` | Residential Property Loan [Member]
Recorded Investment	0	[1]	0	[2]
Unpaid Principal Balance Principal Balance	0		0
Related Allowance	0		0
Average Recorded Investment	0	[3]	0	[4]
Interest Income Recognized	0	[5]	0	[6]
Impaired Mortgage with No Related Allowance [Member]` | Other Collateralized Loans [Member]
Recorded Investment	0	[1]	0	[2]
Unpaid Principal Balance Principal Balance	0		0
Related Allowance	0		0
Average Recorded Investment	0	[3]	0	[4]
Interest Income Recognized	0	[5]	0	[6]
Impaired Mortgage with No Related Allowance [Member]` | Uncollateralized Loans [Member]
Recorded Investment	0	[1]	6	[2]
Unpaid Principal Balance Principal Balance	2		13
Related Allowance	0		0
Average Recorded Investment	4	[3]	6	[4]
Interest Income Recognized	0	[5]	0	[6]
Impaired Mortgage With Related Allowance [Member]
Recorded Investment	219	[1]	553	[2]
Unpaid Principal Balance Principal Balance	219		553
Related Allowance	73		149
Average Recorded Investment	386	[3]	737	[4]
Interest Income Recognized	8	[5]	12	[6]
Impaired Mortgage With Related Allowance [Member] | Commercial Mortgage Loan [Member]
Recorded Investment	185	[1]	513	[2]
Unpaid Principal Balance Principal Balance	185		513
Related Allowance	50		120
Average Recorded Investment	351	[3]	674	[4]
Interest Income Recognized	8	[5]	10	[6]
Impaired Mortgage With Related Allowance [Member] | Agricultural Loan [Member]
Recorded Investment	17	[1]	19	[2]
Unpaid Principal Balance Principal Balance	17		19
Related Allowance	12		11
Average Recorded Investment	16	[3]	14	[4]
Interest Income Recognized	0	[5]	0	[6]
Impaired Mortgage With Related Allowance [Member] | Residential Property Loan [Member]
Recorded Investment	0	[1]	0	[2]
Unpaid Principal Balance Principal Balance	0		0
Related Allowance	0		0
Average Recorded Investment	0	[3]	5	[4]
Interest Income Recognized	0	[5]	0	[6]
Impaired Mortgage With Related Allowance [Member] | Other Collateralized Loans [Member]
Recorded Investment	17	[1]	21	[2]
Unpaid Principal Balance Principal Balance	17		21
Related Allowance	11		18
Average Recorded Investment	19	[3]	31	[4]
Interest Income Recognized	0	[5]	2	[6]
Impaired Mortgage With Related Allowance [Member] | Uncollateralized Loans [Member]
Recorded Investment	0	[1]	0	[2]
Unpaid Principal Balance Principal Balance	0		0
Related Allowance	0		0
Average Recorded Investment	0	[3]	13	[4]
Interest Income Recognized	$ 0	[5]	$ 0	[6]

[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. Average recorded investment represents the average of the beginning-of-period and all subsequent quarterly end-of-period balances. The interest income recognized is for the year-to-date income regardless of when the impairments occurred. Includes the impact of loans acquired from the Star Business for which the balance sheet carrying value had been previously written down.

[3] Average recorded investment represents the average of the beginning-of-period and all subsequent quarterly end-of-period balances. The interest income recognized is for the year-to-date income regardless of when the impairment occurred. Includes the impact of loans acquired from the Star Business for which the balance sheet carrying value had been previously written down.

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

[5] The interest income recognized is for the year-to-date income regardless of when the impairment occurred. Includes the impact of loans acquired from the Star Business for which the balance sheet carrying value had been previously written down.

[6] The interest income recognized is for the year-to-date income regardless of when the impairments occurred.

[7] Includes the impact of loans acquired from the Star Business for which the balance sheet carrying value had been previously written down.

[8] Includes the impact of loans acquired from the Star Business for which the balance sheet carrying value had been previously written down