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Fair Value of Assets & Liabilities - Summary Of Book Value And Estimated Fair Value Of Financial Instruments (Details) - USD ($) $ in Thousands | Mar. 31, 2019 | Dec. 31, 2018
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Total loans, net of unearned income and allowance for loan losses |  | $ 27,805,137 | $ 27,355,108
Short-term financial assets: |  |  |
Interest-bearing cash |  |  | 1,277,611
Federal funds sold |  |  | 237,591
Securities purchased under agreements to resell |  | 474,679 | 386,443
Trading securities |  | 1,681,727 | 1,448,168
Loans held-for-sale | [1] | 594,662 | 679,149
Securities available-for-sale |  | 4,616,322 | 4,626,470
Securities held-to-maturity |  | 10,000 | 10,000
Derivative assets |  | 118,128 | 81,475
Other assets: |  |  |
Total assets |  | 41,099,003 | 40,832,258
Liabilities: |  |  |
Trading Liabilities |  |  | 335,380
Short-term financial liabilities: |  |  |
Federal funds purchased |  |  | 256,567
Securities sold under agreements to repurchase |  | 745,788 | 762,592
Other short-term borrowings |  |  | 114,764
Term borrowings: |  |  |
Other long term borrowings |  | 1,177,926 | 1,170,963
Derivative liabilities |  | 107,123 | 133,713
Total liabilities |  | 36,252,482 | 36,046,878
Fair Value, Inputs, Level 3 | FHLB-Cincinnati Stock |  |  |
Term borrowings: |  |  |
Restricted investments |  | 63,700 | 87,900
Fair Value, Inputs, Level 3 | FRB Stock |  |  |
Term borrowings: |  |  |
Restricted investments |  | 130,700 | 130,700
Reported Value Measurement |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Total loans, net of unearned income and allowance for loan losses |  | 27,805,137 | 27,355,108
Short-term financial assets: |  |  |
Interest-bearing cash |  | 1,013,254 | 1,277,611
Federal funds sold |  | 167,602 | 237,591
Securities purchased under agreements to resell |  | 474,679 | 386,443
Total short-term financial assets |  | 1,655,535 | 1,901,645
Trading securities |  | 1,681,727 | 1,448,168
Loans held-for-sale |  | 594,662 | 679,149
Securities available-for-sale |  | 4,616,322 | 4,626,470
Securities held-to-maturity |  | 10,000 | 10,000
Derivative assets |  | 118,128 | 81,475
Other assets: |  |  |
Tax credit investments |  | 164,509 | 163,300
Deferred compensation assets |  | 41,097 | 37,771
Equity, mutual funds, and other |  | 216,684 | 240,780
Total other assets |  | 422,290 | 441,851
Total assets |  | 36,903,801 | 36,543,866
Liabilities: |  |  |
Defined maturity |  | 4,454,622 | 4,105,777
Trading Liabilities |  | 429,669 | 335,380
Short-term financial liabilities: |  |  |
Federal funds purchased |  | 339,360 | 256,567
Securities sold under agreements to repurchase |  | 745,788 | 762,592
Other short-term borrowings |  | 140,832 | 114,764
Short Term Financial Liabilities |  | 1,225,980 | 1,133,923
Term borrowings: |  |  |
Real estate investment trust-preferred |  | 46,185 | 46,168
Term borrowings - new market tax credit investment |  | 2,699 | 2,699
Secured Borrowings |  | 21,119 | 19,588
Junior subordinated debentures |  | 143,589 | 143,255
Other long term borrowings |  | 964,334 | 959,253
Total term borrowings |  | 1,177,926 | 1,170,963
Derivative liabilities |  | 107,123 | 133,713
Total liabilities |  | 7,395,320 | 6,879,756
Reported Value Measurement | Commercial, financial, and industrial |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Total loans, net of unearned income and allowance for loan losses |  | 17,072,399 | 16,415,381
Reported Value Measurement | Commercial Real Estate |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Total loans, net of unearned income and allowance for loan losses |  | 3,912,561 | 3,999,559
Reported Value Measurement | Consumer Real Estate |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Total loans, net of unearned income and allowance for loan losses |  | 6,127,430 | 6,223,077
Reported Value Measurement | Permanent Mortgage |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Total loans, net of unearned income and allowance for loan losses |  | 199,179 | 211,448
Reported Value Measurement | Credit Card and Other |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Total loans, net of unearned income and allowance for loan losses |  | 493,568 | 505,643
Reported Value Measurement | Mortgage loans (elected fair value) |  |  |
Short-term financial assets: |  |  |
Loans held-for-sale |  | 15,751 | 16,273
Reported Value Measurement | Government guaranteed loans (SBA and USDA) |  |  |
Short-term financial assets: |  |  |
Loans held-for-sale |  | 495,451 | 578,291
Reported Value Measurement | Other consumer loans- LOCOM |  |  |
Short-term financial assets: |  |  |
Loans held-for-sale |  | 24,238 | 25,134
Reported Value Measurement | Mortgage loans- LOCOM |  |  |
Short-term financial assets: |  |  |
Loans held-for-sale |  | 59,222 | 59,451
Estimate of Fair Value Measurement |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Total loans, net of unearned income and allowance for loan losses |  | 27,901,543 | 27,364,329
Short-term financial assets: |  |  |
Interest-bearing cash |  | 1,013,254 | 1,277,611
Federal funds sold |  | 167,602 | 237,591
Securities purchased under agreements to resell |  | 474,679 | 386,443
Total short-term financial assets |  | 1,655,535 | 1,901,645
Trading securities |  | 1,681,727 | 1,448,168
Loans held-for-sale |  | 599,533 | 684,349
Securities available-for-sale |  | 4,616,322 | 4,626,470
Securities held-to-maturity |  | 9,889 | 9,843
Derivative assets |  | 118,128 | 81,475
Other assets: |  |  |
Tax credit investments |  | 161,355 | 159,452
Deferred compensation assets |  | 41,097 | 37,771
Equity, mutual funds, and other |  | 216,684 | 240,780
Total other assets |  | 419,136 | 438,003
Total assets |  | 37,001,813 | 36,554,282
Liabilities: |  |  |
Defined maturity |  | 4,454,687 | 4,082,822
Trading Liabilities |  | 429,669 | 335,380
Short-term financial liabilities: |  |  |
Federal funds purchased |  | 339,360 | 256,567
Securities sold under agreements to repurchase |  | 745,788 | 762,592
Other short-term borrowings |  | 140,832 | 114,764
Short Term Financial Liabilities |  | 1,225,980 | 1,133,923
Term borrowings: |  |  |
Real estate investment trust-preferred |  | 47,000 | 47,000
Term borrowings - new market tax credit investment |  | 2,678 | 2,664
Secured Borrowings |  | 21,119 | 19,588
Junior subordinated debentures |  | 138,947 | 134,266
Other long term borrowings |  | 967,047 | 960,483
Total term borrowings |  | 1,176,791 | 1,164,001
Derivative liabilities |  | 107,123 | 133,713
Total liabilities |  | 7,394,250 | 6,849,839
Loan commitments |  | 2,735 | 2,551
Standby and other commitments |  | 5,052 | 5,043
Estimate of Fair Value Measurement | Commercial, financial, and industrial |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Total loans, net of unearned income and allowance for loan losses |  | 17,166,407 | 16,438,272
Estimate of Fair Value Measurement | Commercial Real Estate |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Total loans, net of unearned income and allowance for loan losses |  | 3,916,819 | 3,997,736
Estimate of Fair Value Measurement | Consumer Real Estate |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Total loans, net of unearned income and allowance for loan losses |  | 6,112,800 | 6,194,066
Estimate of Fair Value Measurement | Permanent Mortgage |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Total loans, net of unearned income and allowance for loan losses |  | 210,387 | 227,254
Estimate of Fair Value Measurement | Credit Card and Other |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Total loans, net of unearned income and allowance for loan losses |  | 495,130 | 507,001
Estimate of Fair Value Measurement | Mortgage loans (elected fair value) |  |  |
Short-term financial assets: |  |  |
Loans held-for-sale |  | 15,751 | 16,273
Estimate of Fair Value Measurement | Government guaranteed loans (SBA and USDA) |  |  |
Short-term financial assets: |  |  |
Loans held-for-sale |  | 500,322 | 583,491
Estimate of Fair Value Measurement | Other consumer loans- LOCOM |  |  |
Short-term financial assets: |  |  |
Loans held-for-sale |  | 24,238 | 25,134
Estimate of Fair Value Measurement | Mortgage loans- LOCOM |  |  |
Short-term financial assets: |  |  |
Loans held-for-sale |  | 59,222 | 59,451
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 1 |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Total loans, net of unearned income and allowance for loan losses |  | 0 | 0
Short-term financial assets: |  |  |
Interest-bearing cash |  | 1,013,254 | 1,277,611
Federal funds sold |  | 0 | 0
Securities purchased under agreements to resell |  | 0 | 0
Total short-term financial assets |  | 1,013,254 | 1,277,611
Trading securities |  | 0 | 0
Loans held-for-sale |  | 0 | 0
Securities available-for-sale |  | 0 | 0
Securities held-to-maturity |  | 0 | 0
Derivative assets |  | 36,976 | 28,826
Other assets: |  |  |
Tax credit investments |  | 0 | 0
Deferred compensation assets |  | 41,097 | 37,771
Equity, mutual funds, and other |  | 22,326 | 22,248
Total other assets |  | 63,423 | 60,019
Total assets |  | 1,113,653 | 1,366,456
Liabilities: |  |  |
Defined maturity |  | 0 | 0
Trading Liabilities |  | 0 | 0
Short-term financial liabilities: |  |  |
Federal funds purchased |  | 0 | 0
Securities sold under agreements to repurchase |  | 0 | 0
Other short-term borrowings |  | 0 | 0
Short Term Financial Liabilities |  | 0 | 0
Term borrowings: |  |  |
Real estate investment trust-preferred |  | 0 | 0
Term borrowings - new market tax credit investment |  | 0 | 0
Secured Borrowings |  | 0 | 0
Junior subordinated debentures |  | 0 | 0
Other long term borrowings |  | 0 | 0
Total term borrowings |  | 0 | 0
Derivative liabilities |  | 36,688 | 30,236
Total liabilities |  | 36,688 | 30,236
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 1 | Commercial, financial, and industrial |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Total loans, net of unearned income and allowance for loan losses |  | 0 | 0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 1 | Commercial Real Estate |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Total loans, net of unearned income and allowance for loan losses |  | 0 | 0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 1 | Consumer Real Estate |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Total loans, net of unearned income and allowance for loan losses |  | 0 | 0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 1 | Permanent Mortgage |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Total loans, net of unearned income and allowance for loan losses |  | 0 | 0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 1 | Credit Card and Other |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Total loans, net of unearned income and allowance for loan losses |  | 0 | 0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 1 | Mortgage loans (elected fair value) |  |  |
Short-term financial assets: |  |  |
Loans held-for-sale |  | 0 | 0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 1 | Government guaranteed loans (SBA and USDA) |  |  |
Short-term financial assets: |  |  |
Loans held-for-sale |  | 0 | 0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 1 | Other consumer loans- LOCOM |  |  |
Short-term financial assets: |  |  |
Loans held-for-sale |  | 0 | 0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 1 | Mortgage loans- LOCOM |  |  |
Short-term financial assets: |  |  |
Loans held-for-sale |  | 0 | 0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 2 |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Total loans, net of unearned income and allowance for loan losses |  | 0 | 0
Short-term financial assets: |  |  |
Interest-bearing cash |  | 0 | 0
Federal funds sold |  | 167,602 | 237,591
Securities purchased under agreements to resell |  | 474,679 | 386,443
Total short-term financial assets |  | 642,281 | 624,034
Trading securities |  | 1,680,330 | 1,446,644
Loans held-for-sale |  | 505,408 | 588,898
Securities available-for-sale |  | 4,603,127 | 4,616,568
Securities held-to-maturity |  | 0 | 0
Derivative assets |  | 81,152 | 52,649
Other assets: |  |  |
Tax credit investments |  | 0 | 0
Deferred compensation assets |  | 0 | 0
Equity, mutual funds, and other |  | 0 | 0
Total other assets |  | 0 | 0
Total assets |  | 7,512,298 | 7,328,793
Liabilities: |  |  |
Defined maturity |  | 4,454,687 | 4,082,822
Trading Liabilities |  | 429,669 | 335,380
Short-term financial liabilities: |  |  |
Federal funds purchased |  | 339,360 | 256,567
Securities sold under agreements to repurchase |  | 745,788 | 762,592
Other short-term borrowings |  | 140,832 | 114,764
Short Term Financial Liabilities |  | 1,225,980 | 1,133,923
Term borrowings: |  |  |
Real estate investment trust-preferred |  | 0 | 0
Term borrowings - new market tax credit investment |  | 0 | 0
Secured Borrowings |  | 0 | 0
Junior subordinated debentures |  | 0 | 0
Other long term borrowings |  | 967,047 | 960,483
Total term borrowings |  | 967,047 | 960,483
Derivative liabilities |  | 41,465 | 71,937
Total liabilities |  | 7,118,848 | 6,584,545
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 2 | Commercial, financial, and industrial |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Total loans, net of unearned income and allowance for loan losses |  | 0 | 0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 2 | Commercial Real Estate |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Total loans, net of unearned income and allowance for loan losses |  | 0 | 0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 2 | Consumer Real Estate |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Total loans, net of unearned income and allowance for loan losses |  | 0 | 0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 2 | Permanent Mortgage |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Total loans, net of unearned income and allowance for loan losses |  | 0 | 0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 2 | Credit Card and Other |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Total loans, net of unearned income and allowance for loan losses |  | 0 | 0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 2 | Mortgage loans (elected fair value) |  |  |
Short-term financial assets: |  |  |
Loans held-for-sale |  | 0 | 0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 2 | Government guaranteed loans (SBA and USDA) |  |  |
Short-term financial assets: |  |  |
Loans held-for-sale |  | 499,307 | 582,476
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 2 | Other consumer loans- LOCOM |  |  |
Short-term financial assets: |  |  |
Loans held-for-sale |  | 6,101 | 6,422
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 2 | Mortgage loans- LOCOM |  |  |
Short-term financial assets: |  |  |
Loans held-for-sale |  | 0 | 0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3 |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Total loans, net of unearned income and allowance for loan losses |  | 27,901,543 | 27,364,329
Short-term financial assets: |  |  |
Interest-bearing cash |  | 0 | 0
Federal funds sold |  | 0 | 0
Securities purchased under agreements to resell |  | 0 | 0
Total short-term financial assets |  | 0 | 0
Trading securities |  | 1,397 | 1,524
Loans held-for-sale |  | 94,125 | 95,451
Securities available-for-sale |  | 13,195 | 9,902
Securities held-to-maturity |  | 9,889 | 9,843
Derivative assets |  | 0 | 0
Other assets: |  |  |
Tax credit investments |  | 161,355 | 159,452
Deferred compensation assets |  | 0 | 0
Equity, mutual funds, and other |  | 194,358 | 218,532
Total other assets |  | 355,713 | 377,984
Total assets |  | 28,375,862 | 27,859,033
Liabilities: |  |  |
Defined maturity |  | 0 | 0
Trading Liabilities |  | 0 | 0
Short-term financial liabilities: |  |  |
Federal funds purchased |  | 0 | 0
Securities sold under agreements to repurchase |  | 0 | 0
Other short-term borrowings |  | 0 | 0
Short Term Financial Liabilities |  | 0 | 0
Term borrowings: |  |  |
Real estate investment trust-preferred |  | 47,000 | 47,000
Term borrowings - new market tax credit investment |  | 2,678 | 2,664
Secured Borrowings |  | 21,119 | 19,588
Junior subordinated debentures |  | 138,947 | 134,266
Other long term borrowings |  | 0 | 0
Total term borrowings |  | 209,744 | 203,518
Derivative liabilities |  | 28,970 | 31,540
Total liabilities |  | 238,714 | 235,058
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3 | Commercial, financial, and industrial |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Total loans, net of unearned income and allowance for loan losses |  | 17,166,407 | 16,438,272
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3 | Commercial Real Estate |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Total loans, net of unearned income and allowance for loan losses |  | 3,916,819 | 3,997,736
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3 | Consumer Real Estate |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Total loans, net of unearned income and allowance for loan losses |  | 6,112,800 | 6,194,066
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3 | Permanent Mortgage |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Total loans, net of unearned income and allowance for loan losses |  | 210,387 | 227,254
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3 | Credit Card and Other |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Total loans, net of unearned income and allowance for loan losses |  | 495,130 | 507,001
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3 | Mortgage loans (elected fair value) |  |  |
Short-term financial assets: |  |  |
Loans held-for-sale |  | 15,751 | 16,273
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3 | Government guaranteed loans (SBA and USDA) |  |  |
Short-term financial assets: |  |  |
Loans held-for-sale |  | 1,015 | 1,015
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3 | Other consumer loans- LOCOM |  |  |
Short-term financial assets: |  |  |
Loans held-for-sale |  | 18,137 | 18,712
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3 | Mortgage loans- LOCOM |  |  |
Short-term financial assets: |  |  |
Loans held-for-sale |  | 59,222 | 59,451
Contractual Amount |  |  |
Term borrowings: |  |  |
Loan commitments |  | 11,000,220 | 10,884,975
Standby and other commitments |  | $ 404,249 | $ 446,958
[1] | March 31, 2019 and December 31, 2018 include $8.0 million and $8.4 million, respectively, of held-for-sale consumer mortgage loans secured by residential real estate in process of foreclosure.

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- Definition Borrowings Secured By Residential Real Estate + References No definition available. + Details
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- Definition Defined maturity deposits include all certificates of deposit and other time deposits. The fair value is estimated by discounting future cash flows to their present value. Future cash flows are discounted by using the current market rates of similar instruments applicable to the remaining maturity. + References No definition available. + Details
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- Definition Tax credit investments in other assets + References No definition available. + Details
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Balance Type: | debit
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- Definition Real estate investment trust-preferred. + References No definition available. + Details
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Balance Type: | credit
Period Type: | instant

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- Definition Short-term financial assets include federal funds sold, securities purchased under agreements to resell, and interest bearing deposits with other financial institutions. + References No definition available. + Details
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Namespace Prefix: | fhn_
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Balance Type: | debit
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- References No definition available. + Details
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- Definition Short-term financial liabilities include federal funds purchased, securities sold under agreements to repurchase, and other short-term borrowings. The carrying amount is a reasonable estimate of fair value because of the relatively short time between the origination of the instrument and its expected realization. Other short-term borrowings includes a liability associated with transfers of mortgage servicing rights that did not qualify for sale accounting. This liability is accounted for at elected fair value, which is measured consistent with the related MSR. + References No definition available. + Details
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- References No definition available. + Details
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- Definition Standby commitments may be provided to customers in order to guarantee payment between a customer and a third party - generally to facilitate trade. Fair values are based on fees charged to enter into similar agreements. + References No definition available. + Details
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- Definition Term borrowings, new market tax credit investment. + References No definition available. + Details
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Namespace Prefix: | fhn_
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Balance Type: | credit
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