Quarterly report pursuant to Section 13 or 15(d)

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

v3.5.0.2
Changes in Level 3 Instruments Measured on a Recurring Basis (Detail) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Sep. 30, 2016
Sep. 30, 2015
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Beginning Balance $ 22 $ 48 $ 32 $ 64
Transfers into (out of) Level 3 0 0 0 0
Net realized and unrealized gains (losses):        
Included in earnings (in investment income) (4) (8) (14) (24)
Included in accumulated other comprehensive income (pre-tax) 0 0 0 0
Purchases 0 0 0 0
Sales 0 0 0 0
Ending Balance 18 40 18 40
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 22 48 32 64
Transfers into (out of) Level 3 0 0 0 0
Net realized and unrealized gains (losses):        
Included in earnings (in investment income) (4) (8) (14) (24)
Included in accumulated other comprehensive income (pre-tax) 0 0 0 0
Purchases 0 0 0 0
Sales 0 0 0 0
Ending Balance $ 18 $ 40 $ 18 $ 40