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LOANS AND LEASES - Additional Allowance for Credit Losses Relating to Acquired Loans (Detail) - USD ($) $ in Millions | Jun. 30, 2019 | Mar. 31, 2019 | Dec. 31, 2018 | Jun. 30, 2018 | Mar. 31, 2018 | Dec. 31, 2017
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Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |  |  |
Total allowance on loans acquired in a business combination | $ 188 | $ 186 | $ 180 | $ 177 | $ 179 | $ 175
Loans Acquired in a Business Combination [Member] |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |  |  |
Total allowance on loans acquired in a business combination | 5 |  | 7 | $ 4 |  | $ 7
Loans Acquired in a Business Combination [Member] | Commercial Real Estate [Member] |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |  |  |
Total allowance on loans acquired in a business combination | 2 |  | 2 |  |  |
Loans Acquired in a Business Combination [Member] | Commercial and Industrial [Member] |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |  |  |
Total allowance on loans acquired in a business combination | 1 |  | 4 |  |  |
Loans Acquired in a Business Combination [Member] | Total Commercial Loans [Member] |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |  |  |
Total allowance on loans acquired in a business combination | 3 |  | 6 |  |  |
Loans Acquired in a Business Combination [Member] | Direct Installment [Member] |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |  |  |
Total allowance on loans acquired in a business combination | 1 |  | 1 |  |  |
Loans Acquired in a Business Combination [Member] | Consumer Loan [Member] |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |  |  |
Total allowance on loans acquired in a business combination | 2 |  | 1 |  |  |
Loans Acquired in a Business Combination [Member] | Residential Mortgages [Member] |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |  |  |
Total allowance on loans acquired in a business combination | $ 1 |  | $ 0 |  |  |

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Definition Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.7(d)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953423-111524 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (b)(1)(ii) -URI http://asc.fasb.org/extlink&oid=118939070&loc=d3e15032-111544 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953423-111524 Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section S99 -Paragraph 4 -Subparagraph (SAB Topic 6.L.1) -URI http://asc.fasb.org/extlink&oid=27010918&loc=d3e74567-122707 + Details
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