SECURITIES - Amortized Cost and Fair Value of Securities Available for Sale (Detail) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 3,268	$ 3,401
Gross Unrealized Gains	23	5
Gross Unrealized Losses	(12)	(65)
Total securities available for sale, fair value	3,279	3,341
US Government Agencies [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	172	188
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	(1)
Total securities available for sale, fair value	172	187
U.S. Government-Sponsored Entities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	301	317
Gross Unrealized Gains	1	0
Gross Unrealized Losses	(1)	(4)
Total securities available for sale, fair value	301	313
Agency Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,318	1,465
Gross Unrealized Gains	3	0
Gross Unrealized Losses	(6)	(36)
Total securities available for sale, fair value	1,315	1,429
Agency Collateralized Mortgage Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,233	1,179
Gross Unrealized Gains	14	5
Gross Unrealized Losses	(5)	(23)
Total securities available for sale, fair value	1,242	1,161
Commercial Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	227	229
Gross Unrealized Gains	5	0
Gross Unrealized Losses	0	(1)
Total securities available for sale, fair value	232	228
States of the U.S. and Political Subdivisions [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	15	21
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Total securities available for sale, fair value	15	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).

+ References

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-Publisher FASB
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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
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
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-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
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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
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=118942338&loc=SL82898722-210454

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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