Loans and Allowance for Credit Losses for Loans - Past Due, Non-Accrual and Current Loans by Loan Portfolio Class (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Financing Receivable, Past Due [Line Items]
Loans	$ 35,364,405	$ 34,153,657
Non-Accrual Loans	230,458	240,216
Non-Accrual Loans Without Allowance for Loan Losses	93,762	100,190
Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans	323,245	296,080
30-59  Days  Past Due Loans
Financing Receivable, Past Due [Line Items]
Loans	54,366	40,889
60-89  Days  Past Due Loans
Financing Receivable, Past Due [Line Items]
Loans	27,014	12,204
90 Days or More Past Due Loans
Financing Receivable, Past Due [Line Items]
Loans	11,407	2,771
Current Loans
Financing Receivable, Past Due [Line Items]
Loans	35,041,160	33,857,577
Commercial and industrial
Financing Receivable, Past Due [Line Items]
Loans	5,791,390	5,847,551
Non-Accrual Loans	96,631	99,918
Non-Accrual Loans Without Allowance for Loan Losses	8,341	9,066
Commercial and industrial | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans	127,076	115,778
Commercial and industrial | 30-59  Days  Past Due Loans
Financing Receivable, Past Due [Line Items]
Loans	6,723	6,717
Commercial and industrial | 60-89  Days  Past Due Loans
Financing Receivable, Past Due [Line Items]
Loans	14,461	7,870
Commercial and industrial | 90 Days or More Past Due Loans
Financing Receivable, Past Due [Line Items]
Loans	9,261	1,273
Commercial and industrial | Current Loans
Financing Receivable, Past Due [Line Items]
Loans	5,664,314	5,731,773
Commercial real estate
Financing Receivable, Past Due [Line Items]
Loans	21,937,744	20,790,066
Non-Accrual Loans	96,798	101,233
Non-Accrual Loans Without Allowance for Loan Losses	66,191	70,719
Commercial real estate | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans	138,752	117,627
Commercial real estate | 30-59  Days  Past Due Loans
Financing Receivable, Past Due [Line Items]
Loans	32,515	16,362
Commercial real estate | 60-89  Days  Past Due Loans
Financing Receivable, Past Due [Line Items]
Loans	9,439	0
Commercial real estate | 90 Days or More Past Due Loans
Financing Receivable, Past Due [Line Items]
Loans	0	32
Commercial real estate | Current Loans
Financing Receivable, Past Due [Line Items]
Loans	21,798,992	20,672,439
Commercial real estate | Commercial real estate
Financing Receivable, Past Due [Line Items]
Loans	19,763,202	18,935,486
Non-Accrual Loans	79,180	83,592
Non-Accrual Loans Without Allowance for Loan Losses	66,191	70,719
Commercial real estate | Commercial real estate | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans	116,301	98,045
Commercial real estate | Commercial real estate | 30-59  Days  Past Due Loans
Financing Receivable, Past Due [Line Items]
Loans	30,807	14,421
Commercial real estate | Commercial real estate | 60-89  Days  Past Due Loans
Financing Receivable, Past Due [Line Items]
Loans	6,314	0
Commercial real estate | Commercial real estate | 90 Days or More Past Due Loans
Financing Receivable, Past Due [Line Items]
Loans	0	32
Commercial real estate | Commercial real estate | Current Loans
Financing Receivable, Past Due [Line Items]
Loans	19,646,901	18,837,441
Commercial real estate | Construction
Financing Receivable, Past Due [Line Items]
Loans	2,174,542	1,854,580
Non-Accrual Loans	17,618	17,641
Non-Accrual Loans Without Allowance for Loan Losses	0	0
Commercial real estate | Construction | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans	22,451	19,582
Commercial real estate | Construction | 30-59  Days  Past Due Loans
Financing Receivable, Past Due [Line Items]
Loans	1,708	1,941
Commercial real estate | Construction | 60-89  Days  Past Due Loans
Financing Receivable, Past Due [Line Items]
Loans	3,125	0
Commercial real estate | Construction | 90 Days or More Past Due Loans
Financing Receivable, Past Due [Line Items]
Loans	0	0
Commercial real estate | Construction | Current Loans
Financing Receivable, Past Due [Line Items]
Loans	2,152,091	1,834,998
Residential mortgage
Financing Receivable, Past Due [Line Items]
Loans	4,691,935	4,545,064
Non-Accrual Loans	33,275	35,207
Non-Accrual Loans Without Allowance for Loan Losses	19,227	20,401
Residential mortgage | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans	46,847	50,197
Residential mortgage | 30-59  Days  Past Due Loans
Financing Receivable, Past Due [Line Items]
Loans	9,266	10,999
Residential mortgage | 60-89  Days  Past Due Loans
Financing Receivable, Past Due [Line Items]
Loans	2,560	3,314
Residential mortgage | 90 Days or More Past Due Loans
Financing Receivable, Past Due [Line Items]
Loans	1,746	677
Residential mortgage | Current Loans
Financing Receivable, Past Due [Line Items]
Loans	4,645,088	4,494,867
Consumer
Financing Receivable, Past Due [Line Items]
Loans	2,943,336	2,970,976
Non-Accrual Loans	3,754	3,858
Non-Accrual Loans Without Allowance for Loan Losses	3	4
Consumer | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans	10,570	12,478
Consumer | 30-59  Days  Past Due Loans
Financing Receivable, Past Due [Line Items]
Loans	5,862	6,811
Consumer | 60-89  Days  Past Due Loans
Financing Receivable, Past Due [Line Items]
Loans	554	1,020
Consumer | 90 Days or More Past Due Loans
Financing Receivable, Past Due [Line Items]
Loans	400	789
Consumer | Current Loans
Financing Receivable, Past Due [Line Items]
Loans	2,932,766	2,958,498
Consumer | Home equity
Financing Receivable, Past Due [Line Items]
Loans	393,538	400,779
Non-Accrual Loans	3,382	3,517
Non-Accrual Loans Without Allowance for Loan Losses	3	4
Consumer | Home equity | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans	3,462	3,857
Consumer | Home equity | 30-59  Days  Past Due Loans
Financing Receivable, Past Due [Line Items]
Loans	38	242
Consumer | Home equity | 60-89  Days  Past Due Loans
Financing Receivable, Past Due [Line Items]
Loans	42	98
Consumer | Home equity | 90 Days or More Past Due Loans
Financing Receivable, Past Due [Line Items]
Loans	0	0
Consumer | Home equity | Current Loans
Financing Receivable, Past Due [Line Items]
Loans	390,076	396,922
Consumer | Automobile
Financing Receivable, Past Due [Line Items]
Loans	1,552,928	1,570,036
Non-Accrual Loans	273	240
Non-Accrual Loans Without Allowance for Loan Losses	0	0
Consumer | Automobile | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans	5,422	7,558
Consumer | Automobile | 30-59  Days  Past Due Loans
Financing Receivable, Past Due [Line Items]
Loans	4,687	6,391
Consumer | Automobile | 60-89  Days  Past Due Loans
Financing Receivable, Past Due [Line Items]
Loans	458	656
Consumer | Automobile | 90 Days or More Past Due Loans
Financing Receivable, Past Due [Line Items]
Loans	4	271
Consumer | Automobile | Current Loans
Financing Receivable, Past Due [Line Items]
Loans	1,547,506	1,562,478
Consumer | Other consumer
Financing Receivable, Past Due [Line Items]
Loans	996,870	1,000,161
Non-Accrual Loans	99	101
Non-Accrual Loans Without Allowance for Loan Losses	0	0
Consumer | Other consumer | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans	1,686	1,063
Consumer | Other consumer | 30-59  Days  Past Due Loans
Financing Receivable, Past Due [Line Items]
Loans	1,137	178
Consumer | Other consumer | 60-89  Days  Past Due Loans
Financing Receivable, Past Due [Line Items]
Loans	54	266
Consumer | Other consumer | 90 Days or More Past Due Loans
Financing Receivable, Past Due [Line Items]
Loans	396	518
Consumer | Other consumer | Current Loans
Financing Receivable, Past Due [Line Items]
Loans	$ 995,184	$ 999,098