Annual report pursuant to Section 13 and 15(d)

LONG-TERM DEBT - Schedule of Long-Term Debt (Details)

v3.10.0.1
LONG-TERM DEBT - Schedule of Long-Term Debt (Details) - USD ($)
$ in Millions
 3 Months Ended 12 Months Ended
Dec. 31, 2018
Dec. 31, 2018
Dec. 31, 2017
Debt Instrument [Line Items]      
Long-term borrowings $ 8,625 $ 8,625 $ 9,206
Subordinated Notes      
Debt Instrument [Line Items]      
Long-term borrowings 4,957 4,957 5,733
Subordinated Notes | 3.86% Huntington National Bank subordinated notes due 2026 [Member]      
Debt Instrument [Line Items]      
Long-term borrowings $ 229 $ 229 238
Stated rate 3.86% 3.86%  
Subordinated Notes | 5.45% Huntington National Bank subordinated notes due 2019      
Debt Instrument [Line Items]      
Long-term borrowings $ 76 $ 76 77
Stated rate 5.45% 5.45%  
Subordinated Notes | 6.67% Huntington National Bank subordinated notes due 2026      
Debt Instrument [Line Items]      
Long-term borrowings $ 0 $ 0 129
Stated rate 6.67% 6.67%  
Senior Notes | 3.55% Huntington National Bank senior notes due 2023      
Debt Instrument [Line Items]      
Long-term borrowings $ 756 $ 756 0
Stated rate 3.55% 3.55%  
Senior Notes | 3.25% Huntington National Bank senior notes due 2021      
Debt Instrument [Line Items]      
Long-term borrowings $ 750 $ 750 0
Stated rate 3.25% 3.25%  
Senior Notes | 2.47% Huntington National Bank senior notes due 2020      
Debt Instrument [Line Items]      
Long-term borrowings $ 692 $ 692 694
Stated rate 2.47% 2.47%  
Senior Notes | 2.55% Huntington National Bank senior notes due 2022      
Debt Instrument [Line Items]      
Long-term borrowings $ 672 $ 672 685
Stated rate 2.50% 2.50%  
Senior Notes | 2.23% Huntington National Bank senior note due 2019      
Debt Instrument [Line Items]      
Long-term borrowings $ 498 $ 498 497
Stated rate 2.23% 2.23%  
Senior Notes | 2.43% Huntington National Bank senior notes due 2020      
Debt Instrument [Line Items]      
Long-term borrowings $ 493 $ 493 498
Stated rate 2.43% 2.43%  
Senior Notes | 2.97% Huntington National Bank senior notes due 2020      
Debt Instrument [Line Items]      
Long-term borrowings $ 491 $ 491 492
Stated rate 2.97% 2.97%  
Senior Notes | 3.31% Huntington National Bank senior notes due 2020 (5)      
Debt Instrument [Line Items]      
Long-term borrowings $ 300 $ 300 300
Effective rate 3.31% 3.31%  
Senior Notes | 2.24% Huntington National Bank senior notes due 2018      
Debt Instrument [Line Items]      
Long-term borrowings $ 0 $ 0 844
Stated rate 2.24% 2.24%  
Senior Notes | 2.10% Huntington National Bank senior notes due 2018      
Debt Instrument [Line Items]      
Long-term borrowings $ 0 $ 0 748
Stated rate 2.10% 2.10%  
Senior Notes | 1.75% Huntington National Bank senior notes due 2018      
Debt Instrument [Line Items]      
Long-term borrowings $ 0 $ 0 496
Stated rate 1.75% 1.75%  
Senior Notes | 5.04% Huntington National Bank medium-term notes due 2018      
Debt Instrument [Line Items]      
Long-term borrowings $ 0 $ 0 35
Federal Home Loan Bank advances      
Debt Instrument [Line Items]      
Long-term borrowings 6 6 7
Other borrowings      
Debt Instrument [Line Items]      
Long-term borrowings $ 446 $ 446 338
Other borrowings | Federal Home Loan Bank advances      
Debt Instrument [Line Items]      
Effective rate 3.12% 3.12%  
Other borrowings | Huntington Technology Finance nonrecourse debt, 4.19% effective interest rate, varying maturities      
Debt Instrument [Line Items]      
Long-term borrowings $ 322 $ 322 263
Effective rate 4.19% 4.19%  
Other borrowings | 4.68% Huntington Preferred Capital II - Class F securities      
Debt Instrument [Line Items]      
Long-term borrowings $ 74 $ 74 75
Effective rate 4.68% 4.68%  
Other borrowings | 4.68% Huntington Preferred Capital II - Class G securities      
Debt Instrument [Line Items]      
Long-term borrowings $ 50 $ 50 0
Effective rate 4.68% 4.68%  
Other borrowings | London Interbank Offered Rate (LIBOR) [Member] | 4.68% Huntington Preferred Capital II - Class F securities      
Debt Instrument [Line Items]      
Basis spread on variable rate   1.88%  
Parent Company      
Debt Instrument [Line Items]      
Long-term borrowings $ 3,216 $ 3,216 3,128
Parent Company | Subordinated Notes | 7.00% Huntington Bancshares Incorporated subordinated notes due 2020      
Debt Instrument [Line Items]      
Long-term borrowings $ 305 $ 305 312
Stated rate 7.00% 7.00%  
Parent Company | Subordinated Notes | 3.55% Huntington Bancshares Incorporated subordinated notes due 2023      
Debt Instrument [Line Items]      
Long-term borrowings $ 239 $ 239 245
Stated rate 3.55% 3.55%  
Parent Company | Subordinated Notes | Sky Financial Capital Trust IV 4.20% junior subordinated debentures due 2036      
Debt Instrument [Line Items]      
Long-term borrowings $ 74 $ 74 74
Effective rate 4.20% 4.20%  
Parent Company | Subordinated Notes | Sky Financial Capital Trust III 4.20% junior subordinated debentures due 2036      
Debt Instrument [Line Items]      
Long-term borrowings $ 72 $ 72 72
Effective rate 4.20% 4.20%  
Parent Company | Subordinated Notes | Huntington Capital I Trust Preferred 3.50% junior subordinated debentures due 2027      
Debt Instrument [Line Items]      
Long-term borrowings $ 69 $ 69 69
Effective rate 3.50% 3.50%  
Parent Company | Subordinated Notes | Huntington Capital II Trust Preferred 3.42% junior subordinated debentures due 2028      
Debt Instrument [Line Items]      
Long-term borrowings $ 31 $ 31 31
Effective rate 3.42% 3.42%  
Parent Company | Subordinated Notes | Camco Statutory Trust I 4.13% due 2037      
Debt Instrument [Line Items]      
Long-term borrowings $ 4 $ 4 4
Effective rate 4.13% 4.13%  
Parent Company | Subordinated Notes | London Interbank Offered Rate (LIBOR) [Member] | Sky Financial Capital Trust IV 4.20% junior subordinated debentures due 2036      
Debt Instrument [Line Items]      
Basis spread on variable rate   1.40%  
Parent Company | Subordinated Notes | London Interbank Offered Rate (LIBOR) [Member] | Sky Financial Capital Trust III 4.20% junior subordinated debentures due 2036      
Debt Instrument [Line Items]      
Basis spread on variable rate 1.40%    
Parent Company | Subordinated Notes | London Interbank Offered Rate (LIBOR) [Member] | Huntington Capital I Trust Preferred 3.50% junior subordinated debentures due 2027      
Debt Instrument [Line Items]      
Basis spread on variable rate   0.70%  
Parent Company | Subordinated Notes | London Interbank Offered Rate (LIBOR) [Member] | Huntington Capital II Trust Preferred 3.42% junior subordinated debentures due 2028      
Debt Instrument [Line Items]      
Basis spread on variable rate   0.625%  
Parent Company | Subordinated Notes | London Interbank Offered Rate (LIBOR) [Member] | Camco Statutory Trust I 4.13% due 2037      
Debt Instrument [Line Items]      
Basis spread on variable rate   1.33%  
Parent Company | Subordinated Notes | London Interbank Offered Rate (LIBOR) [Member] | 3.31% Huntington National Bank senior notes due 2020 (5)      
Debt Instrument [Line Items]      
Basis spread on variable rate   0.51%  
Parent Company | Senior Notes | 3.19% Huntington Bancshares Incorporated medium-term notes due 2021      
Debt Instrument [Line Items]      
Long-term borrowings $ 969 $ 969 969
Stated rate 3.19% 3.19%  
Parent Company | Senior Notes | 2.33% Huntington Bancshares Incorporated senior notes due 2022      
Debt Instrument [Line Items]      
Long-term borrowings $ 946 $ 946 953
Stated rate 2.33% 2.33%  
Parent Company | Senior Notes | 4.00% Huntington Bancshares Incorporated senior notes due 2025      
Debt Instrument [Line Items]      
Long-term borrowings $ 507 $ 507 0
Stated rate 4.00% 4.00%  
Parent Company | Senior Notes | 2.64% Huntington Bancshares Incorporated senior notes due 2018      
Debt Instrument [Line Items]      
Long-term borrowings $ 0 $ 0 $ 399
Stated rate 2.64% 2.64%