Premises and Equipment - Narrative (Details)		12 Months Ended
	Nov. 12, 2021 USD ($)	Dec. 31, 2021 USD ($) branch	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Property, Plant and Equipment [Line Items]
Depreciation		$ 12,000,000	$ 13,000,000	$ 15,900,000
Premises transferred to held for sale		$ 37,600,000	0
Number of branch locations transferred to held for sale | branch		5
Gain (loss) on properties transferred to held for sale		$ 1,200,000
Proceeds from sale of premises held for sale		21,981,000	0	0
Gain (loss) on disposition of property plant equipment		(4,715,000)	$ (73,000)	$ (271,000)
Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations
Property, Plant and Equipment [Line Items]
Gain (loss) on disposition of property plant equipment		$ 0
Century Bancorp, Inc.
Property, Plant and Equipment [Line Items]
Number of branch locations transferred to held for sale | branch		4
Gain (loss) on disposition of property plant equipment	$ 0