Recently Issued Accounting Pronouncements Impact of Recently Issued Accounting Pronouncements (Detail) - USD ($) $ in Millions	Jan. 01, 2017	Jan. 01, 2016
Impact of Recently Adopted Accounting Pronouncements [Abstract]
Cumulative Effect of New Accounting Principle in Period of Adoption	$ 1	$ 5

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