Allowance for Credit Losses - Credit Risk Profiles Based on Payment Activity, Not Subject to Loan Grading (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Loans and Leases Receivable Disclosure [Line Items]
Loans and leases	$ 13,279,097	$ 13,211,650	$ 13,076,191
Residential and consumer
Loans and Leases Receivable Disclosure [Line Items]
Loans and leases		6,282,731
Residential and consumer | Performing
Loans and Leases Receivable Disclosure [Line Items]
Loans and leases		6,229,130
Residential and consumer | Non-performing and delinquent
Loans and Leases Receivable Disclosure [Line Items]
Loans and leases		53,601
Residential
Loans and Leases Receivable Disclosure [Line Items]
Loans and leases	3,690,218	4,662,175	4,439,618
Residential | Residential mortgage
Loans and Leases Receivable Disclosure [Line Items]
Loans and leases		3,768,936
Residential | Residential mortgage | Performing
Loans and Leases Receivable Disclosure [Line Items]
Loans and leases		3,759,799
Residential | Residential mortgage | Non-performing and delinquent
Loans and Leases Receivable Disclosure [Line Items]
Loans and leases		9,137
Home equity Line
Loans and Leases Receivable Disclosure [Line Items]
Loans and leases	841,624
Home equity Line | Home equity
Loans and Leases Receivable Disclosure [Line Items]
Loans and leases		893,239
Home equity Line | Home equity | Performing
Loans and Leases Receivable Disclosure [Line Items]
Loans and leases		886,879
Home equity Line | Home equity | Non-performing and delinquent
Loans and Leases Receivable Disclosure [Line Items]
Loans and leases		6,360
Consumer
Loans and Leases Receivable Disclosure [Line Items]
Loans and leases	$ 1,353,842	1,620,556	$ 1,662,504
Consumer | Consumer loans
Loans and Leases Receivable Disclosure [Line Items]
Loans and leases		226,304
Consumer | Consumer loans | Performing
Loans and Leases Receivable Disclosure [Line Items]
Loans and leases		219,046
Consumer | Consumer loans | Non-performing and delinquent
Loans and Leases Receivable Disclosure [Line Items]
Loans and leases		7,258
Consumer | Consumer - Auto
Loans and Leases Receivable Disclosure [Line Items]
Loans and leases		1,040,468
Consumer | Consumer - Auto | Performing
Loans and Leases Receivable Disclosure [Line Items]
Loans and leases		1,016,142
Consumer | Consumer - Auto | Non-performing and delinquent
Loans and Leases Receivable Disclosure [Line Items]
Loans and leases		24,326
Consumer | Credit Cards
Loans and Leases Receivable Disclosure [Line Items]
Loans and leases		353,784
Consumer | Credit Cards | Performing
Loans and Leases Receivable Disclosure [Line Items]
Loans and leases		347,264
Consumer | Credit Cards | Non-performing and delinquent
Loans and Leases Receivable Disclosure [Line Items]
Loans and leases		$ 6,520