Derivative Instruments (Balance Sheet Offsetting) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Financial Assets
Derivative Instruments, Gross amount of recognized assets	$ 2,117	$ 3,547
Derivative Instruments, Gross amounts offset	(1,003)	(895)
Derivative Instruments, Net amount of assets	1,114	2,652
Derivative Instruments, Cash collateral received	(1,006)	(2,624)
Derivative Instruments, Net amount	108	28
Embedded Derivative Instruments, Gross amount of recognized assets	711
Embedded Derivative Instruments, Gross amounts offset
Embedded Derivative Instruments, Net amount of assets	711
Embedded Derivative Instruments, Cash collateral received
Embedded Derivative Instruments, Net amount	711
Securities Lending and Reverse Repurchase Agreements, Gross amount of recognized assets
Securities Lending and Reverse Repurchase Agreements, Gross amounts offset
Securities Lending and Reverse Repurchase Agreements, Net amount of assets
Securities Lending and Reverse Repurchase Agreements, Cash collateral received
Securities Lending and Reverse Repurchase Agreements, Net amount
Total, Gross amount of recognized assets	2,828	3,547
Total, Gross amounts offset	(1,003)	(895)
Total, Net amount of assets	1,825	2,652
Total, Cash collateral received	(1,006)	(2,624)
Total, Net amount	819	28
Securities Purchased under Agreements to Resell, Gross
Financial Liabilities
Derivative Instruments, Gross amount of recognized liabilities	1,008	906
Derivative Instruments, Gross amounts offset	(1,003)	(895)
Derivative Instruments, Net amount of liabilities	5	11
Derivative Instruments, Financial instruments
Derivative Instruments, Net amount	5	11
Embedded Derivative Instruments, Gross amount of recognized liabilities	1,045	1,856
Embedded Derivative Instruments, Gross amounts offset
Embedded Derivative Instruments, Net amount of liabilities	1,045	1,856
Embedded Derivative Instruments, Financial instruments
Embedded Derivative Instruments, Net amount	1,045	1,856
Securities Lending and Reverse Repurchase Agreements, Gross amount of recognized liabilities	2,596	1,614
Securities Lending and Reverse Repurchase Agreements, Gross amounts offset
Securities Lending and Reverse Repurchase Agreements, Net amount of liabilities	2,596	1,614
Securities Lending and Reverse Repurchase Agreements, Financial instruments	(2,596)	(1,614)
Securities Lending and Reverse Repurchase Agreements, Net amount
Total, Gross amount of recognized liabilities	4,649	4,376
Total, Gross amounts offset	(1,003)	(895)
Total, Net amount of liabilities	3,646	3,481
Total, Financial instruments	(2,596)	(1,614)
Total, Net amount	$ 1,050	$ 1,867