Quarterly report pursuant to Section 13 or 15(d)

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

v2.4.0.6
Changes in Level 3 Instruments Measured on a Recurring Basis (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended
Mar. 31, 2013
Mar. 31, 2012
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning Balance $ 163 $ 217
Transfers into (out of) Level 3 0 0
Net realized and unrealized gains (losses):    
Included in earnings (in investment income) (13) (13)
Included in accumulated other comprehensive income (pre-tax) 0 0
Purchases 0 0
Sales 0 0
Ending Balance 150 204
Marketable securities
   
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning Balance 0 0
Transfers into (out of) Level 3 0 0
Net realized and unrealized gains (losses):    
Included in earnings (in investment income) 0 0
Included in accumulated other comprehensive income (pre-tax) 0 0
Purchases 0 0
Sales 0 0
Ending Balance 0 0
Other Long-term Investments
   
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning Balance 163 217
Transfers into (out of) Level 3 0 0
Net realized and unrealized gains (losses):    
Included in earnings (in investment income) (13) (13)
Included in accumulated other comprehensive income (pre-tax) 0 0
Purchases 0 0
Sales 0 0
Ending Balance $ 150 $ 204