Derivative Instruments (Balance Sheet Offsetting) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Financial Assets
Derivative Instruments, Gross amount of recognized assets	$ 1,848	$ 1,805
Derivative Instruments, Gross amounts offset	(804)	(924)
Derivative Instruments, Net amount of assets	1,044	881
Derivative Instruments, Cash collateral received	(877)	(623)
Derivative Instruments, Net amount	167	258
Embedded Derivative Instruments, Gross amount of recognized assets	1,022	1,244
Embedded Derivative Instruments, Gross amounts offset
Embedded Derivative Instruments, Net amount of assets	1,022	1,244
Embedded Derivative Instruments, Cash collateral received
Embedded Derivative Instruments, Net amount	1,022	1,244
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	2,870	3,049
Total, Gross amounts offset	(804)	(924)
Total, Net amount of assets	2,066	2,125
Total, Cash collateral received	(877)	(623)
Total, Net amount	1,189	1,502
Securities Purchased under Agreements to Resell, Gross
Financial Liabilities
Derivative Instruments, Gross amount of recognized liabilities	193	242
Derivative Instruments, Gross amounts offset	(75)	(55)
Derivative Instruments, Net amount of liabilities	118	187
Derivative Instruments, Net amount	118	187
Embedded Derivative Instruments, Gross amount of recognized liabilities	1,268	1,156
Embedded Derivative Instruments, Gross amounts offset
Embedded Derivative Instruments, Net amount of liabilities	1,268	1,156
Embedded Derivative Instruments, Net amount	1,268	1,156
Securities Lending and Reverse Repurchase Agreements, Gross amount of recognized liabilities	2,573	2,600
Securities Lending and Reverse Repurchase Agreements, Gross amounts offset
Securities Lending and Reverse Repurchase Agreements, Net amount of liabilities	2,573	2,600
Securities Lending and Reverse Repurchase Agreements, Cash collateral received	(2,573)	(2,600)
Securities Lending and Reverse Repurchase Agreements, Net amount
Total, Gross amount of recognized liabilities	4,034	3,998
Total, Gross amounts offset	(75)	(55)
Total, Net amount of liabilities	3,959	3,943
Total, Cash collateral received	(2,573)	(2,600)
Total, Net amount	$ 1,386	$ 1,343