Quarterly report pursuant to Section 13 or 15(d)

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

v3.8.0.1
Changes in Level 3 Instruments Measured on a Recurring Basis (Detail) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Beginning Balance $ 9 $ 22 $ 13 $ 32
Transfers into (out of) Level 3 0 0 0 0
Net realized and unrealized gains (losses):        
Included in earnings (in investment income and other) (1) (4) (5) (14)
Included in accumulated other comprehensive income (pre-tax) 0 0 0 0
Purchases 0 0 0 0
Sales 0 0 0 0
Ending Balance 8 18 8 18
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 and other) 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 Non-Current Investments        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Beginning Balance 9 22 13 32
Transfers into (out of) Level 3 0 0 0 0
Net realized and unrealized gains (losses):        
Included in earnings (in investment income and other) (1) (4) (5) (14)
Included in accumulated other comprehensive income (pre-tax) 0 0 0 0
Purchases 0 0 0 0
Sales 0 0 0 0
Ending Balance $ 8 $ 18 $ 8 $ 18