Quarterly report pursuant to Section 13 or 15(d)

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

v3.7.0.1
Changes in Level 3 Instruments Measured on a Recurring Basis (Detail) - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2017
Mar. 31, 2016
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning Balance $ 13 $ 32
Transfers into (out of) Level 3 0 0
Net realized and unrealized gains (losses):    
Included in earnings (in investment income) (2) (5)
Included in accumulated other comprehensive income (pre-tax) 0 0
Purchases 0 0
Sales 0 0
Ending Balance 11 27
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 13 32
Transfers into (out of) Level 3 0 0
Net realized and unrealized gains (losses):    
Included in earnings (in investment income) (2) (5)
Included in accumulated other comprehensive income (pre-tax) 0 0
Purchases 0 0
Sales 0 0
Ending Balance $ 11 $ 27