SECURITIES - Amortized Cost and Fair Value of Securities Available for Sale (Detail) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 3,203	$ 3,275
Gross Unrealized Gains	99	24
Gross Unrealized Losses	(1)	(10)
Total securities available for sale, fair value	3,301	3,289
U.S. Treasury [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	300
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Total securities available for sale, fair value	300
US Government Agencies [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	153	152
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1)	(1)
Total securities available for sale, fair value	152	151
U.S. Government-Sponsored Entities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	155	225
Gross Unrealized Gains	2	1
Gross Unrealized Losses	0	0
Total securities available for sale, fair value	157	226
Agency Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,156	1,310
Gross Unrealized Gains	44	7
Gross Unrealized Losses	0	(3)
Total securities available for sale, fair value	1,200	1,314
Agency Collateralized Mortgage Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,045	1,234
Gross Unrealized Gains	35	10
Gross Unrealized Losses	0	(4)
Total securities available for sale, fair value	1,080	1,240
Commercial Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	385	341
Gross Unrealized Gains	18	6
Gross Unrealized Losses	0	(2)
Total securities available for sale, fair value	403	345
States of the U.S. and Political Subdivisions (municipals) [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	7	11
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Total securities available for sale, fair value	7	11
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).

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-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
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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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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
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