Loans and Allowances for Credit Losses, By Aging Category (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Financing Receivable, Past Due [Line Items]
Past Due 90 Days or More and Accruing	$ 87,473	$ 119,132
Current and Past Due Performing Loans	21,291,148	20,205,680
30 to 59 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	50,069	43,102
60 to 89 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	25,005	27,870
90 Days or More [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	123,397	153,861
Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	21,092,677	19,980,847
Commercial [Member]
Financing Receivable, Past Due [Line Items]
Past Due 90 Days or More and Accruing	0	199
Current and Past Due Performing Loans	13,578,697	12,506,465
Commercial [Member] | 30 to 59 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	2,865	9,904
Commercial [Member] | 60 to 89 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	1,444	9,333
Commercial [Member] | 90 Days or More [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	14,598	14,298
Commercial [Member] | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	13,559,790	12,472,930
Commercial [Member] | Energy [Member]
Financing Receivable, Past Due [Line Items]
Past Due 90 Days or More and Accruing	0	0
Current and Past Due Performing Loans	3,393,072	3,006,884
Commercial [Member] | Energy [Member] | 30 to 59 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	0	545
Commercial [Member] | Energy [Member] | 60 to 89 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	0	3,716
Commercial [Member] | Energy [Member] | 90 Days or More [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	0	0
Commercial [Member] | Energy [Member] | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	3,393,072	3,002,623
Commercial [Member] | Healthcare [Member]
Financing Receivable, Past Due [Line Items]
Past Due 90 Days or More and Accruing	0	0
Current and Past Due Performing Loans	3,696,963	3,414,940
Commercial [Member] | Healthcare [Member] | 30 to 59 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	2,178	2,359
Commercial [Member] | Healthcare [Member] | 60 to 89 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	0	0
Commercial [Member] | Healthcare [Member] | 90 Days or More [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	6,529	509
Commercial [Member] | Healthcare [Member] | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	3,688,256	3,412,072
Commercial [Member] | Services [Member]
Financing Receivable, Past Due [Line Items]
Past Due 90 Days or More and Accruing	0	0
Current and Past Due Performing Loans	3,421,493	3,367,193
Commercial [Member] | Services [Member] | 30 to 59 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	198	920
Commercial [Member] | Services [Member] | 60 to 89 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	0	4,620
Commercial [Member] | Services [Member] | 90 Days or More [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	8,069	9,014
Commercial [Member] | Services [Member] | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	3,413,226	3,352,639
Commercial [Member] | General business [Member]
Financing Receivable, Past Due [Line Items]
Past Due 90 Days or More and Accruing	0	199
Current and Past Due Performing Loans	3,067,169	2,717,448
Commercial [Member] | General business [Member] | 30 to 59 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	489	6,080
Commercial [Member] | General business [Member] | 60 to 89 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	1,444	997
Commercial [Member] | General business [Member] | 90 Days or More [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	0	4,775
Commercial [Member] | General business [Member] | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	3,065,236	2,705,596
Commercial real estate [Member]
Financing Receivable, Past Due [Line Items]
Past Due 90 Days or More and Accruing	0	0
Current and Past Due Performing Loans	4,106,148	3,831,325
Commercial real estate [Member] | 30 to 59 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	28	0
Commercial real estate [Member] | 60 to 89 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	0	206
Commercial real estate [Member] | 90 Days or More [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	3,200	3,157
Commercial real estate [Member] | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	4,102,920	3,827,962
Paycheck Protection Program [Member]
Financing Receivable, Past Due [Line Items]
Past Due 90 Days or More and Accruing	3	74
Current and Past Due Performing Loans	43,140	276,341
Paycheck Protection Program [Member] | 30 to 59 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	27	0
Paycheck Protection Program [Member] | 60 to 89 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	459	0
Paycheck Protection Program [Member] | 90 Days or More [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	3	0
Paycheck Protection Program [Member] | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	42,651	276,341
Loans to individuals [Member]
Financing Receivable, Past Due [Line Items]
Past Due 90 Days or More and Accruing	87,470	118,859
Current and Past Due Performing Loans	3,563,163	3,591,549
Loans to individuals [Member] | 30 to 59 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	47,149	33,198
Loans to individuals [Member] | 60 to 89 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	23,102	18,331
Loans to individuals [Member] | 90 Days or More [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	105,596	136,406
Loans to individuals [Member] | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	3,387,316	3,403,614
Loans to individuals [Member] | Residential mortgage [Member]
Financing Receivable, Past Due [Line Items]
Past Due 90 Days or More and Accruing	0	0
Current and Past Due Performing Loans	1,784,729	1,722,170
Loans to individuals [Member] | Residential mortgage [Member] | 30 to 59 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	10,904	6,263
Loans to individuals [Member] | Residential mortgage [Member] | 60 to 89 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	1,828	1,556
Loans to individuals [Member] | Residential mortgage [Member] | 90 Days or More [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	5,643	6,697
Loans to individuals [Member] | Residential mortgage [Member] | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	1,766,354	1,707,654
Loans to individuals [Member] | Residential mortgage [Member] | US Government Agency Insured Loans [Member]
Financing Receivable, Past Due [Line Items]
Past Due 90 Days or More and Accruing	87,470	118,819
Current and Past Due Performing Loans	293,838	354,173
Loans to individuals [Member] | Residential mortgage [Member] | US Government Agency Insured Loans [Member] | 30 to 59 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	35,574	26,869
Loans to individuals [Member] | Residential mortgage [Member] | US Government Agency Insured Loans [Member] | 60 to 89 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	19,659	16,751
Loans to individuals [Member] | Residential mortgage [Member] | US Government Agency Insured Loans [Member] | 90 Days or More [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	99,930	129,531
Loans to individuals [Member] | Residential mortgage [Member] | US Government Agency Insured Loans [Member] | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	138,675	181,022
Loans to individuals [Member] | Personal [Member]
Financing Receivable, Past Due [Line Items]
Past Due 90 Days or More and Accruing	0	40
Current and Past Due Performing Loans	1,484,596	1,515,206
Loans to individuals [Member] | Personal [Member] | 30 to 59 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	671	66
Loans to individuals [Member] | Personal [Member] | 60 to 89 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	1,615	24
Loans to individuals [Member] | Personal [Member] | 90 Days or More [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	23	178
Loans to individuals [Member] | Personal [Member] | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	$ 1,482,287	$ 1,514,938