Quarterly report pursuant to Section 13 or 15(d)

Changes in Level 3 Instruments Measured on a Recurring Basis (Detail)

v2.4.0.8
Changes in Level 3 Instruments Measured on a Recurring Basis (Detail) (USD $)
In Millions, unless otherwise specified
 3 Months Ended 9 Months Ended
Sep. 30, 2014
Sep. 30, 2013
Sep. 30, 2014
Sep. 30, 2013
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Beginning Balance $ 95 $ 136 $ 110 $ 163
Transfers into (out of) Level 3 0 0 0 0
Net realized and unrealized gains (losses):        
Included in earnings (in investment income) (11) (13) (26) (40)
Included in accumulated other comprehensive income (pre-tax) 0 0 0 0
Purchases 0 0 0 0
Sales 0 0 0 0
Ending Balance 84 123 84 123
Marketable securities
        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Beginning Balance 0 0 0 0
Transfers into (out of) Level 3 0 0 0 0
Net realized and unrealized gains (losses):        
Included in earnings (in investment income) 0 0 0 0
Included in accumulated other comprehensive income (pre-tax) 0 0 0 0
Purchases 0 0 0 0
Sales 0 0 0 0
Ending Balance 0 0 0 0
Other Long-term Investments
        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Beginning Balance 95 136 110 163
Transfers into (out of) Level 3 0 0 0 0
Net realized and unrealized gains (losses):        
Included in earnings (in investment income) (11) (13) (26) (40)
Included in accumulated other comprehensive income (pre-tax) 0 0 0 0
Purchases 0 0 0 0
Sales 0 0 0 0
Ending Balance $ 84 $ 123 $ 84 $ 123