Statutory Financial Information (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Parent Company [Member]
Summarize the statutory net income (loss) and statutory capital and surplus for the Company and its primary insurance subsidiary
Statutory Net Income(Loss)	$ 711	$ 1,039	$ 751
Statutory capital and surplus	6,845	5,949	5,208
Subsidiaries [Member]
Summarize the statutory net income (loss) and statutory capital and surplus for the Company and its primary insurance subsidiary
Statutory Net Income(Loss)	230	(277)	(227)
Statutory capital and surplus	1,468	1,340	$ 968
Subsidiaries One [Member]
Summarize the statutory net income (loss) and statutory capital and surplus for the Company and its primary insurance subsidiary
Statutory Net Income(Loss)	7
Statutory capital and surplus	43	35
Subsidiaries Two [Member]
Summarize the statutory net income (loss) and statutory capital and surplus for the Company and its primary insurance subsidiary
Statutory capital and surplus	$ 7	$ 7

Schedule Of Statutory Net Income Loss And Statutory Capital And Surplus [Abstract]

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- Definition

The amount of statutory capital and surplus (stockholders' equity) as of the balance sheet date using prescribed or permitted statutory accounting practices (rather than GAAP, if different) of the state or country.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(23)(c))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 505
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6486098&loc=d3e24708-158529

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- Definition

Amount of net income for the period determined using accounting principles prescribed or permitted by insurance regulators.

+ References

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