Loans - Schedule of Loan Assigned Risk Rating within 12 Months of Balance Sheet Date (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Jan. 01, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Amount of recorded investment	$ 3,337,449	$ 2,804,035	$ 2,784,562
Commercial, industrial, and agricultural
Financing Receivable, Credit Quality Indicator [Line Items]
Amount of recorded investment		1,046,665
Commercial mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Amount of recorded investment		$ 814,002
Internal Noninvestment Grade
Financing Receivable, Credit Quality Indicator [Line Items]
Amount of recorded investment			1,860,667
Internal Noninvestment Grade | Commercial, industrial, and agricultural
Financing Receivable, Credit Quality Indicator [Line Items]
Amount of recorded investment			1,046,665
Internal Noninvestment Grade | Commercial mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Amount of recorded investment			814,002
Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Amount of recorded investment			1,785,243
Pass | Commercial, industrial, and agricultural
Financing Receivable, Credit Quality Indicator [Line Items]
Amount of recorded investment			1,004,445
Pass | Commercial mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Amount of recorded investment			780,798
Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Amount of recorded investment			35,533
Special Mention | Commercial, industrial, and agricultural
Financing Receivable, Credit Quality Indicator [Line Items]
Amount of recorded investment			16,696
Special Mention | Commercial mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Amount of recorded investment			18,837
Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Amount of recorded investment			39,891
Substandard | Commercial, industrial, and agricultural
Financing Receivable, Credit Quality Indicator [Line Items]
Amount of recorded investment			25,524
Substandard | Commercial mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Amount of recorded investment			14,367
Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Amount of recorded investment			0
Doubtful | Commercial, industrial, and agricultural
Financing Receivable, Credit Quality Indicator [Line Items]
Amount of recorded investment			0
Doubtful | Commercial mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Amount of recorded investment			$ 0