SECURITIES - Amortized Cost and Fair Value of Securities Available for Sale (Detail) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 3,244	$ 3,401
Gross Unrealized Gains	28	5
Gross Unrealized Losses	(10)	(65)
Total securities available for sale, fair value	3,262	3,341
US Government Agencies [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	159	188
Gross Unrealized Gains	1	0
Gross Unrealized Losses	(1)	(1)
Total securities available for sale, fair value	159	187
U.S. Government-Sponsored Entities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	245	317
Gross Unrealized Gains	1	0
Gross Unrealized Losses	(1)	(4)
Total securities available for sale, fair value	245	313
Agency Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,337	1,465
Gross Unrealized Gains	5	0
Gross Unrealized Losses	(4)	(36)
Total securities available for sale, fair value	1,338	1,429
Agency Collateralized Mortgage Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,178	1,179
Gross Unrealized Gains	13	5
Gross Unrealized Losses	(3)	(23)
Total securities available for sale, fair value	1,188	1,161
Commercial Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	309	229
Gross Unrealized Gains	8	0
Gross Unrealized Losses	(1)	(1)
Total securities available for sale, fair value	316	228
States of the U.S. and Political Subdivisions [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	14	21
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Total securities available for sale, fair value	14	21
Other Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2	2
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Total securities available for sale, fair value	$ 2	$ 2

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 50
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-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563

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-Publisher FASB
-Name Accounting Standards Codification
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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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-URI http://asc.fasb.org/extlink&oid=118942338&loc=SL82898722-210454

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