Loans and Allowances for Credit Losses, By Aging Category (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Financing Receivable, Past Due [Line Items]
Past Due 90 Days or More and Accruing	$ 65,056	$ 76,114
Current and Past Due Performing Loans	22,750,053	22,557,150
30 to 59 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	74,016	55,039
60 to 89 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	613	51,614
90 Days or More [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	110,990	94,633
Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	22,564,434	22,355,864
Commercial [Member]
Financing Receivable, Past Due [Line Items]
Past Due 90 Days or More and Accruing	54	396
Current and Past Due Performing Loans	14,217,349	14,212,499
Commercial [Member] | 30 to 59 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	7,336	7,255
Commercial [Member] | 60 to 89 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	62	30,365
Commercial [Member] | 90 Days or More [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	32,489	5,813
Commercial [Member] | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	14,177,462	14,169,066
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	3,398,057	3,424,790
Commercial [Member] | Energy [Member] | 30 to 59 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	0	24
Commercial [Member] | Energy [Member] | 60 to 89 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	0	0
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	3,398,057	3,424,766
Commercial [Member] | Healthcare [Member]
Financing Receivable, Past Due [Line Items]
Past Due 90 Days or More and Accruing	45	0
Current and Past Due Performing Loans	3,899,341	3,845,017
Commercial [Member] | Healthcare [Member] | 30 to 59 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	0	5,914
Commercial [Member] | Healthcare [Member] | 60 to 89 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	0	26,480
Commercial [Member] | Healthcare [Member] | 90 Days or More [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	32,420	459
Commercial [Member] | Healthcare [Member] | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	3,866,921	3,812,164
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	3,563,702	3,431,521
Commercial [Member] | Services [Member] | 30 to 59 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	6,844	1,060
Commercial [Member] | Services [Member] | 60 to 89 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	45	2,461
Commercial [Member] | Services [Member] | 90 Days or More [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	60	4,958
Commercial [Member] | Services [Member] | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	3,556,753	3,423,042
Commercial [Member] | General business [Member]
Financing Receivable, Past Due [Line Items]
Past Due 90 Days or More and Accruing	9	396
Current and Past Due Performing Loans	3,356,249	3,511,171
Commercial [Member] | General business [Member] | 30 to 59 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	492	257
Commercial [Member] | General business [Member] | 60 to 89 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	17	1,424
Commercial [Member] | General business [Member] | 90 Days or More [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	9	396
Commercial [Member] | General business [Member] | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	3,355,731	3,509,094
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	4,815,316	4,606,777
Commercial real estate [Member] | 30 to 59 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	8,965	531
Commercial real estate [Member] | 60 to 89 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	45	0
Commercial real estate [Member] | 90 Days or More [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	0	217
Commercial real estate [Member] | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	4,806,306	4,606,029
Loans to individuals [Member]
Financing Receivable, Past Due [Line Items]
Past Due 90 Days or More and Accruing	65,002	75,718
Current and Past Due Performing Loans	3,717,388	3,737,874
Loans to individuals [Member] | 30 to 59 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	57,715	47,253
Loans to individuals [Member] | 60 to 89 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	506	21,249
Loans to individuals [Member] | 90 Days or More [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	78,501	88,603
Loans to individuals [Member] | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	3,580,666	3,580,769
Loans to individuals [Member] | Residential mortgage [Member]
Financing Receivable, Past Due [Line Items]
Past Due 90 Days or More and Accruing	22	114
Current and Past Due Performing Loans	1,926,027	1,890,784
Loans to individuals [Member] | Residential mortgage [Member] | 30 to 59 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	8,315	10,632
Loans to individuals [Member] | Residential mortgage [Member] | 60 to 89 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	363	1,828
Loans to individuals [Member] | Residential mortgage [Member] | 90 Days or More [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	6,550	6,169
Loans to individuals [Member] | Residential mortgage [Member] | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	1,910,799	1,872,155
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	64,980	75,604
Current and Past Due Performing Loans	224,753	245,940
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	48,833	36,119
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	0	19,400
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	71,928	82,402
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	103,992	108,019
Loans to individuals [Member] | Personal [Member]
Financing Receivable, Past Due [Line Items]
Past Due 90 Days or More and Accruing	0	0
Current and Past Due Performing Loans	1,566,608	1,601,150
Loans to individuals [Member] | Personal [Member] | 30 to 59 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	567	502
Loans to individuals [Member] | Personal [Member] | 60 to 89 Days [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	143	21
Loans to individuals [Member] | Personal [Member] | 90 Days or More [Member]
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	23	32
Loans to individuals [Member] | Personal [Member] | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Current and Past Due Performing Loans	$ 1,565,875	$ 1,600,595