Quarterly report pursuant to Section 13 or 15(d)

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

v2.3.0.15
Changes in Level 3 Instruments Measured on a Recurring Basis (Detail) (USD $)
In Millions
3 Months Ended 9 Months Ended
Sep. 30, 2011
Sep. 30, 2011
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Beginning Balance $ 240 $ 405
Transfers into (out of) Level 3    
Net realized and unrealized gains (losses):    
Included in earnings (in investment income) (12) (39)
Included in accumulated other comprehensive income (pre-tax)    
Purchases    
Sales   (138)
Ending Balance 228 228
Marketable securities
   
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Beginning Balance   138
Transfers into (out of) Level 3    
Net realized and unrealized gains (losses):    
Included in accumulated other comprehensive income (pre-tax)    
Purchases    
Sales   (138)
Other Long-term Investments
   
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Beginning Balance 240 267
Transfers into (out of) Level 3    
Net realized and unrealized gains (losses):    
Included in earnings (in investment income) (12) (39)
Included in accumulated other comprehensive income (pre-tax)    
Purchases    
Ending Balance $ 228 $ 228