Fair Value Measurements - Changes in Level 3 Financial Liabilities (Details) (Derivative Financial Instruments, Liabilities [Member], Guaranteed Minimum Income Benefit [Member], USD $)
In Millions, unless otherwise specified
 3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Derivative Financial Instruments, Liabilities [Member] | Guaranteed Minimum Income Benefit [Member]
    
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance $ (929) $ (741)
Gains (losses) included in shareholders' net income:    
GMIB fair value gain/(loss) (27) (77)
Other (1) 12
Total gains (losses) included in shareholders' net income (28) (65)
Gains (losses) included in other comprehensive income 0 0
Gains (losses) required to adjust future policy benefits for settlement annuities 0 [1] 0 [1]
Purchases, issuances, settlements:    
Purchases 0 0
Sales 0 0
Settlements 9 12
Total purchases, sales, and settlements 9 12
Transfers into/(out of) Level 3:    
Transfers into Level 3 0 0
Transfers out of Level 3 0 0
Transfers into/(out of) Level 3 0 0
Ending balance (948) (794)
Total gains (losses) included in income attributable to instruments held at the reporting date $ (28) $ (65)
[1] Amounts do not accrue to shareholders.