Schedule IV - (Reinsurance) (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Supplemental Schedule of Reinsurance Premiums for Insurance Companies [Abstract]
Direct Amount	$ 3	$ 3	$ (1)
Ceded to Others		1	1
Net Amount	$ 3	$ 2	$ (2)
Percentage of Amount Assumed to Net	0.00%	0.00%	0.00%

Amount, after premiums ceded to other entities and premiums assumed by the entity, of premiums written.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 605
-Section 50
-Paragraph 1
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 605
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547

Name:	us-gaap_PremiumsWrittenNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration