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SECURITIES - Amortized Cost and Fair Value of Securities Held to Maturity (Detail) - USD ($) $ in Millions | Jun. 30, 2019 | Dec. 31, 2018
--- | --- | ---
Investment Securities Held To Maturity [Line Items] |  |
Amortized Cost | $ 3,079 | $ 3,254
Gross Unrealized Gains | 32 | 5
Gross Unrealized Losses | (18) | (104)
Fair Value | 3,093 | 3,155
U.S. Treasury [Member] |  |
Investment Securities Held To Maturity [Line Items] |  |
Amortized Cost | 1 | 1
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | 0 | 0
Fair Value | 1 | 1
US Government Agencies [Member] |  |
Investment Securities Held To Maturity [Line Items] |  |
Amortized Cost | 2 | 2
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | 0 | 0
Fair Value | 2 | 2
U.S. Government-Sponsored Entities [Member] |  |
Investment Securities Held To Maturity [Line Items] |  |
Amortized Cost | 190 | 215
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | (1) | (4)
Fair Value | 189 | 211
Agency Mortgage-Backed Securities [Member] |  |
Investment Securities Held To Maturity [Line Items] |  |
Amortized Cost | 952 | 1,036
Gross Unrealized Gains | 4 | 0
Gross Unrealized Losses | (4) | (26)
Fair Value | 952 | 1,010
Agency Collateralized Mortgage Obligations [Member] |  |
Investment Securities Held To Maturity [Line Items] |  |
Amortized Cost | 728 | 794
Gross Unrealized Gains | 6 | 1
Gross Unrealized Losses | (8) | (24)
Fair Value | 726 | 771
Commercial Mortgage-Backed Securities [Member] |  |
Investment Securities Held To Maturity [Line Items] |  |
Amortized Cost | 100 | 126
Gross Unrealized Gains | 4 | 1
Gross Unrealized Losses | 0 | (1)
Fair Value | 104 | 126
States of the U.S. and Political Subdivisions [Member] |  |
Investment Securities Held To Maturity [Line Items] |  |
Amortized Cost | 1,106 | 1,080
Gross Unrealized Gains | 18 | 3
Gross Unrealized Losses | (5) | (49)
Fair Value | $ 1,119 | $ 1,034

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- Definition Amount of investment in debt security measured at amortized cost (held-to-maturity). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=118954083&loc=d3e26610-111562 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27232-111563 + Details
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- Definition Amount of accumulated unrecognized gain on investment in debt security measured at amortized cost (held-to-maturity). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27232-111563 + Details
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- Definition Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27232-111563 + Details
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- Definition Fair value of investment in debt security measured at amortized cost (held-to-maturity). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27232-111563 + Details
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