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Loans and Allowances for Credit Losses, By Aging Category (Details) - USD ($) | Dec. 31, 2019 | Dec. 31, 2018
--- | --- | ---
Financing receivable, recorded investment, aging [Abstract] |  |
Current | $ 21,392,306,000 | $ 21,308,989,000
Nonaccrual | 180,951,000 | 163,247,000
Total | 21,750,987,000 | 21,656,730,000
Commercial [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Current | 13,899,429,000 | 13,521,894,000
Nonaccrual | 115,416,000 | 99,841,000
Total | 14,031,650,000 | 13,636,078,000
Commercial [Member] | Energy [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Current | 3,881,244,000 | 3,542,839,000
Nonaccrual | 91,722,000 | 47,494,000
Total | 3,973,377,000 | 3,590,333,000
Commercial [Member] | Services [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Current | 3,105,621,000 | 3,237,578,000
Nonaccrual | 7,483,000 | 8,567,000
Total | 3,122,163,000 | 3,258,192,000
Commercial [Member] | Wholesale/retail [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Current | 1,758,878,000 | 1,619,290,000
Nonaccrual | 1,163,000 | 1,316,000
Total | 1,760,866,000 | 1,621,158,000
Commercial [Member] | Manufacturing [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Current | 654,329,000 | 721,204,000
Nonaccrual | 10,133,000 | 8,919,000
Total | 665,449,000 | 730,521,000
Commercial [Member] | Healthcare [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Current | 3,027,329,000 | 2,781,944,000
Nonaccrual | 4,480,000 | 16,538,000
Total | 3,033,916,000 | 2,799,277,000
Commercial [Member] | Public finance [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Current | 707,638,000 | 804,550,000
Nonaccrual | 0 | 0
Total | 709,868,000 | 804,550,000
Commercial [Member] | Other commercial and industrial [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Current | 764,390,000 | 814,489,000
Nonaccrual | 435,000 | 17,007,000
Total | 766,011,000 | 832,047,000
Commercial Real Estate [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Current | 4,400,576,000 | 4,725,669,000
Nonaccrual | 27,626,000 | 21,621,000
Total | 4,433,783,000 | 4,764,813,000
Commercial Real Estate [Member] | Residential construction and land development [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Current | 147,379,000 | 147,705,000
Nonaccrual | 350,000 | 350,000
Total | 150,879,000 | 148,584,000
Commercial Real Estate [Member] | Retail [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Current | 756,653,000 | 884,424,000
Nonaccrual | 18,868,000 | 20,279,000
Total | 775,521,000 | 919,082,000
Commercial Real Estate [Member] | Office [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Current | 928,379,000 | 1,072,920,000
Nonaccrual | 0 | 0
Total | 928,379,000 | 1,072,920,000
Commercial Real Estate [Member] | Multifamily [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Current | 1,258,704,000 | 1,287,483,000
Nonaccrual | 6,858,000 | 301,000
Total | 1,265,562,000 | 1,288,065,000
Commercial Real Estate [Member] | Industrial [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Current | 855,208,000 | 776,898,000
Nonaccrual | 909,000 | 0
Total | 856,117,000 | 778,106,000
Commercial Real Estate [Member] | Other commercial real estate [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Current | 454,253,000 | 556,239,000
Nonaccrual | 641,000 | 691,000
Total | 457,325,000 | 558,056,000
Residential Mortgage [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Current | 1,895,939,000 | 2,037,128,000
Nonaccrual | 37,622,000 | 41,555,000
Total | 2,084,172,000 | 2,230,033,000
Residential Mortgage [Member] | Permanent mortgage [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Current | 1,034,716,000 | 1,095,097,000
Nonaccrual | 20,441,000 | 23,951,000
Total | 1,057,321,000 | 1,122,610,000
Residential Mortgage [Member] | Permanent mortgages guaranteed by U.S. government agencies [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Current | 46,898,000 | 37,459,000
Nonaccrual | 6,100,000 | 7,132,000
Total | 197,794,000 | 190,866,000
Residential Mortgage [Member] | Home equity [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Current | 814,325,000 | 904,572,000
Nonaccrual | 11,081,000 | 10,472,000
Total | 829,057,000 | 916,557,000
Personal [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Current | 1,196,362,000 | 1,024,298,000
Nonaccrual | 287,000 | 230,000
Total | 1,201,382,000 | 1,025,806,000
30 to 59 Days Past Due [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 47,084,000 | 53,350,000
30 to 59 Days Past Due [Member] | Commercial [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 7,943,000 | 7,675,000
30 to 59 Days Past Due [Member] | Commercial [Member] | Energy [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 401,000 | 0
30 to 59 Days Past Due [Member] | Commercial [Member] | Services [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 1,737,000 | 6,009,000
30 to 59 Days Past Due [Member] | Commercial [Member] | Wholesale/retail [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 712,000 | 515,000
30 to 59 Days Past Due [Member] | Commercial [Member] | Manufacturing [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 410,000 | 392,000
30 to 59 Days Past Due [Member] | Commercial [Member] | Healthcare [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 2,039,000 | 241,000
30 to 59 Days Past Due [Member] | Commercial [Member] | Public finance [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 2,230,000 | 0
30 to 59 Days Past Due [Member] | Commercial [Member] | Other commercial and industrial [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 414,000 | 518,000
30 to 59 Days Past Due [Member] | Commercial Real Estate [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 4,920,000 | 16,529,000
30 to 59 Days Past Due [Member] | Commercial Real Estate [Member] | Residential construction and land development [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 3,093,000 | 249,000
30 to 59 Days Past Due [Member] | Commercial Real Estate [Member] | Retail [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 0 | 14,379,000
30 to 59 Days Past Due [Member] | Commercial Real Estate [Member] | Office [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 0 | 0
30 to 59 Days Past Due [Member] | Commercial Real Estate [Member] | Multifamily [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 0 | 281,000
30 to 59 Days Past Due [Member] | Commercial Real Estate [Member] | Industrial [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 0 | 1,208,000
30 to 59 Days Past Due [Member] | Commercial Real Estate [Member] | Other commercial real estate [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 1,827,000 | 412,000
30 to 59 Days Past Due [Member] | Residential Mortgage [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 29,557,000 | 28,667,000
30 to 59 Days Past Due [Member] | Residential Mortgage [Member] | Permanent mortgage [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 2,011,000 | 3,196,000
30 to 59 Days Past Due [Member] | Residential Mortgage [Member] | Permanent mortgages guaranteed by U.S. government agencies [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 24,203,000 | 24,369,000
30 to 59 Days Past Due [Member] | Residential Mortgage [Member] | Home equity [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 3,343,000 | 1,102,000
30 to 59 Days Past Due [Member] | Personal [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 4,664,000 | 479,000
60 to 89 Days Past Due [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 20,560,000 | 24,245,000
60 to 89 Days Past Due [Member] | Commercial [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 1,608,000 | 6,106,000
60 to 89 Days Past Due [Member] | Commercial [Member] | Energy [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 10,000 | 0
60 to 89 Days Past Due [Member] | Commercial [Member] | Services [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 523,000 | 6,038,000
60 to 89 Days Past Due [Member] | Commercial [Member] | Wholesale/retail [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 113,000 | 37,000
60 to 89 Days Past Due [Member] | Commercial [Member] | Manufacturing [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 190,000 | 6,000
60 to 89 Days Past Due [Member] | Commercial [Member] | Healthcare [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 0 | 0
60 to 89 Days Past Due [Member] | Commercial [Member] | Public finance [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 0 | 0
60 to 89 Days Past Due [Member] | Commercial [Member] | Other commercial and industrial [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 772,000 | 25,000
60 to 89 Days Past Due [Member] | Commercial Real Estate [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 250,000 | 280,000
60 to 89 Days Past Due [Member] | Commercial Real Estate [Member] | Residential construction and land development [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 0 | 280,000
60 to 89 Days Past Due [Member] | Commercial Real Estate [Member] | Retail [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 0 | 0
60 to 89 Days Past Due [Member] | Commercial Real Estate [Member] | Office [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 0 | 0
60 to 89 Days Past Due [Member] | Commercial Real Estate [Member] | Multifamily [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 0 | 0
60 to 89 Days Past Due [Member] | Commercial Real Estate [Member] | Industrial [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 0 | 0
60 to 89 Days Past Due [Member] | Commercial Real Estate [Member] | Other commercial real estate [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 250,000 | 0
60 to 89 Days Past Due [Member] | Residential Mortgage [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 18,648,000 | 17,063,000
60 to 89 Days Past Due [Member] | Residential Mortgage [Member] | Permanent mortgage [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 153,000 | 366,000
60 to 89 Days Past Due [Member] | Residential Mortgage [Member] | Permanent mortgages guaranteed by U.S. government agencies [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 18,187,000 | 16,345,000
60 to 89 Days Past Due [Member] | Residential Mortgage [Member] | Home equity [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 308,000 | 352,000
60 to 89 Days Past Due [Member] | Personal [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 54,000 | 796,000
90 Days or More [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 110,086,000 | 106,899,000
90 Days or More [Member] | Commercial [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 7,254,000 | 562,000
90 Days or More [Member] | Commercial [Member] | Energy [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 0 | 0
90 Days or More [Member] | Commercial [Member] | Services [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 6,799,000 | 0
90 Days or More [Member] | Commercial [Member] | Wholesale/retail [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 0 | 0
90 Days or More [Member] | Commercial [Member] | Manufacturing [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 387,000 | 0
90 Days or More [Member] | Commercial [Member] | Healthcare [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 68,000 | 554,000
90 Days or More [Member] | Commercial [Member] | Public finance [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 0 | 0
90 Days or More [Member] | Commercial [Member] | Other commercial and industrial [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 0 | 8,000
90 Days or More [Member] | Commercial Real Estate [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 411,000 | 714,000
90 Days or More [Member] | Commercial Real Estate [Member] | Residential construction and land development [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 57,000 | 0
90 Days or More [Member] | Commercial Real Estate [Member] | Retail [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 0 | 0
90 Days or More [Member] | Commercial Real Estate [Member] | Office [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 0 | 0
90 Days or More [Member] | Commercial Real Estate [Member] | Multifamily [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 0 | 0
90 Days or More [Member] | Commercial Real Estate [Member] | Industrial [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 0 | 0
90 Days or More [Member] | Commercial Real Estate [Member] | Other commercial real estate [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 354,000 | 714,000
90 Days or More [Member] | Residential Mortgage [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 102,406,000 | 105,620,000
90 Days or More [Member] | Residential Mortgage [Member] | Permanent mortgage [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 0 | 0
90 Days or More [Member] | Residential Mortgage [Member] | Permanent mortgages guaranteed by U.S. government agencies [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 102,406,000 | 105,561,000
90 Days or More [Member] | Residential Mortgage [Member] | Home equity [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | 0 | 59,000
90 Days or More [Member] | Personal [Member] |  |
Financing receivable, recorded investment, aging [Abstract] |  |
Past Due | $ 15,000 | $ 3,000

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