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

Basis of Presentation - Additional Information (Detail) - USD ($) $ in Millions	Jan. 01, 2019	Dec. 31, 2017
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Cumulative effect of retained earnings		$ 0
ASC 842
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Cumulative effect of retained earnings	$ 0