Schedule I - Condensed Financial Information of Parent Company - Presentation of Debt Issuance Costs (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Debt Issuance Costs [Line Items]
Other (within investments and other assets)	$ 129	$ 121
Long-term debt	4,656	4,397
Parent Company [Member]
Debt Issuance Costs [Line Items]
Other (within investments and other assets)	127	82
Long-term debt	$ 264	454
As Filed [Member]
Debt Issuance Costs [Line Items]
Other (within investments and other assets)		166
Long-term debt		4,441
As Filed [Member] | Parent Company [Member]
Debt Issuance Costs [Line Items]
Other (within investments and other assets)		84
Long-term debt		456
Scenario, Adjustment [Member]
Debt Issuance Costs [Line Items]
Other (within investments and other assets)		(45)
Long-term debt		(44)
Scenario, Adjustment [Member] | Parent Company [Member]
Debt Issuance Costs [Line Items]
Other (within investments and other assets)		(2)
Long-term debt		$ (2)