Securities (Details)		12 Months Ended
	Jan. 01, 2020 USD ($)	Dec. 31, 2020 USD ($) security	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Debt Securities, Trading, and Equity Securities, FV-NI, Total		$ 0	$ 0
Number of securities in portfolio | security		3
Specific reserve for outstanding balance of financing receivable in active forbearance		$ 600,000
Accrued interest receivable on held-to-maturity securities		100,000
Accrued interest receivable on available-for-sale debt securities		1,300,000
Mortgage Backed Securities Available for Sale Amortized Cost		308,100,000	128,000,000.0	$ 196,400,000
Proceeds from Sale of Debt Securities, Available-for-sale		221,000,000.0	26,400,000	$ 67,000,000.0
Held-to-maturity Securities [Member]
Outstanding balance in active forbearance		21,000,000.0
Non-qualified Deferred Compensation Plan [Member] | Other Assets [Member]
Deferred Compensation Plan, Amounts Held in Rabbi Trust		$ 22,600,000	$ 20,000,000.0
Collateralized Mortgage Obligations by Commercial Real Estate [Member]
Private Issue Collateralized Mortgage Obligations, Number		0	0
Accounting Standards Update 2016-13 [Member]
Increase in allowance for held-to-maturity debt securities	$ 300,000