Goodwill - Goodwill Activity (Parenthetical) (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Goodwill Roll Forward
Excess of tax goodwill over book goodwill	$ 106	$ 137

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

Name:	us-gaap_GoodwillRollForward
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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration