Loans and Allowances for Credit Losses, By Aging Category (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Financing Receivable, Past Due [Line Items]
Past Due 90 Days or More and Accruing	$ 73,148	$ 119,132
Current and Past Due Performing Loans	21,790,457	20,205,680
30 to 59 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	50,576	43,102
60 to 89 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	20,349	27,870
90 Days or More [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	103,257	153,861
Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	21,616,275	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	13,607,686	12,506,465
Commercial [Member] | 30 to 59 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	2,946	9,904
Commercial [Member] | 60 to 89 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	701	9,333
Commercial [Member] | 90 Days or More [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	16,201	14,298
Commercial [Member] | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	13,587,838	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	3,371,588	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	3,371,588	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	3,826,623	3,414,940
Commercial [Member] | Healthcare [Member] | 30 to 59 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	524	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	14,786	509
Commercial [Member] | Healthcare [Member] | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	3,811,313	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	3,280,925	3,367,193
Commercial [Member] | Services [Member] | 30 to 59 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	1,832	920
Commercial [Member] | Services [Member] | 60 to 89 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	154	4,620
Commercial [Member] | Services [Member] | 90 Days or More [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	1,307	9,014
Commercial [Member] | Services [Member] | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	3,277,632	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	3,128,550	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	590	6,080
Commercial [Member] | General business [Member] | 60 to 89 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	547	997
Commercial [Member] | General business [Member] | 90 Days or More [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	108	4,775
Commercial [Member] | General business [Member] | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	3,127,305	2,705,596
Commercial real estate [Member]
Financing Receivable, Past Due [Line Items]
Past Due 90 Days or More and Accruing	101	0
Current and Past Due Performing Loans	4,473,911	3,831,325
Commercial real estate [Member] | 30 to 59 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	0	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	318	3,157
Commercial real estate [Member] | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	4,473,593	3,827,962
Paycheck Protection Program [Member]
Financing Receivable, Past Due [Line Items]
Past Due 90 Days or More and Accruing	19	74
Current and Past Due Performing Loans	20,233	276,341
Paycheck Protection Program [Member] | 30 to 59 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	0	0
Paycheck Protection Program [Member] | 60 to 89 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	3	0
Paycheck Protection Program [Member] | 90 Days or More [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	19	0
Paycheck Protection Program [Member] | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	20,211	276,341
Loans to individuals [Member]
Financing Receivable, Past Due [Line Items]
Past Due 90 Days or More and Accruing	73,028	118,859
Current and Past Due Performing Loans	3,688,627	3,591,549
Loans to individuals [Member] | 30 to 59 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	47,630	33,198
Loans to individuals [Member] | 60 to 89 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	19,645	18,331
Loans to individuals [Member] | 90 Days or More [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	86,719	136,406
Loans to individuals [Member] | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	3,534,633	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	1,851,836	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	5,203	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	1,397	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	5,219	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	1,840,017	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	73,028	118,819
Current and Past Due Performing Loans	262,466	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	40,778	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	18,248	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	81,474	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	121,966	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	1,574,325	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	1,649	66
Loans to individuals [Member] | Personal [Member] | 60 to 89 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	0	24
Loans to individuals [Member] | Personal [Member] | 90 Days or More [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	26	178
Loans to individuals [Member] | Personal [Member] | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	$ 1,572,650	$ 1,514,938