Goodwill and other intangibles (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 159,595,000	$ 159,595,000	$ 159,595,000	$ 159,595,000	$ 159,595,000	$ 159,595,000	$ 159,595,000	$ 159,595,000
Other Intangible Assets, Net	7,882,000	9,785,000	7,882,000	9,785,000	8,302,000	9,260,000	10,310,000	11,523,000
Amortization of Intangible Assets	420,000	525,000	1,378,000	1,738,000
Finite-lived Intangible Assets Acquired	14,456,000		14,456,000			14,456,000
Indefinite-lived Intangible Assets Acquired	1,300,000		1,300,000			1,300,000
Finite-Lived Intangible Assets, Accumulated Amortization	7,874,000		7,874,000			6,496,000
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	420,000		420,000
Finite-Lived Intangible Assets, Amortization Expense, Year Two	1,487,000		1,487,000
Finite-Lived Intangible Assets, Amortization Expense, Year Three	1,323,000		1,323,000
Finite-Lived Intangible Assets, Amortization Expense, Year Four	1,215,000		1,215,000
Finite-Lived Intangible Assets, Amortization Expense, Year Five	1,042,000		1,042,000
Intangible Assets, Gross (Excluding Goodwill)	15,756,000		15,756,000			15,756,000
Intangible Assets, Net (Including Goodwill)	167,477,000	$ 169,380,000	167,477,000	$ 169,380,000	$ 167,897,000	168,855,000	$ 169,905,000	$ 171,118,000
Core Deposits [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Accumulated Amortization	6,574,000		6,574,000			5,196,000
Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Accumulated Amortization	$ 1,300,000		$ 1,300,000			$ 1,300,000