Condensed Financial Information (Parent Company) (Investment in Subsidiaries Footnote) (Detail) (Notes) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2017	Dec. 31, 2017
Condensed Financial Statements, Captions [Line Items]
Capital contributions	$ (202)
Parent Company
Condensed Financial Statements, Captions [Line Items]
Capital contributions		$ 83
Cash dividends received from subsidiaries		544
Parent Company \| Brighthouse Life Insurance Co of NY
Condensed Financial Statements, Captions [Line Items]
Capital contributions		75
Parent Company \| Brighthouse Reinsurance Company of Delaware
Condensed Financial Statements, Captions [Line Items]
Cash dividends received from subsidiaries		$ 535

This element represents disclosure of the total aggregate cash dividends paid to the entity by consolidated subsidiaries, by unconsolidated subsidiaries, and by 50% or less owned persons accounted for using the equity method.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-04(b))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24072-122690

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 235
-Section S99
-Paragraph 2
-Subparagraph (SX 210.9-06)
-URI http://asc.fasb.org/extlink&oid=6882215&loc=d3e537971-122884

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration