Commitments (Activity in Reserve for Representation and Warranty Provisions) (Detail) - Residential Mortgage - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Valuation And Qualifying Accounts Disclosure
Balance, beginning of period	$ 9	$ 13
Net (reductions) additions to the reserve	(3)	(3)
Losses charged against the reserve	0	(1)
Balance, end of period	$ 6	$ 9

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No definition available.

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- Definition

Amount of valuation and qualifying accounts and reserves.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SX 210.12-09)
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690

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- Definition

Amount of decrease in valuation and qualifying accounts and reserves.

+ References

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- Definition

Amount of increase (decrease) in valuation and qualifying accounts and reserves.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SX 210.12-09)
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690

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