Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption.

No definition available.

Name:	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Summary of Significant Accounting Policies (Detail) - Effect of Early Adoption of New Accounting Pronouncement - Accounting Standards Update 2016-09 - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2016	Dec. 31, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Excess tax benefit recognized in provision	$ (10)	$ (27)
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reduction to retained earnings			$ 7