Goodwill and other intangibles (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 159,595,000	$ 157,999,000	$ 159,595,000	$ 157,999,000	$ 159,595,000	$ 159,595,000	$ 158,057,000	$ 112,739,000
Other Intangible Assets, Net	9,785,000	15,490,000	9,785,000	15,490,000	10,310,000	11,523,000	16,231,000	6,971,000
Goodwill, Acquired During Period	0		0	45,260,000
Indefinite-lived Intangible Assets Acquired	0	0	0	10,251,000
Acquired goodwill and intangibles	0		0	55,511,000
Amortization of Intangible Assets	525,000	741,000	1,738,000	1,732,000
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	5,971,000		5,971,000			4,233,000
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	525,000		525,000
Finite-Lived Intangible Assets, Amortization Expense, Year Two	1,798,000		1,798,000
Finite-Lived Intangible Assets, Amortization Expense, Year Three	1,487,000		1,487,000
Finite-Lived Intangible Assets, Amortization Expense, Year Four	1,323,000		1,323,000
Finite-Lived Intangible Assets, Amortization Expense, Year Five	1,215,000		1,215,000
Intangible Assets, Gross (Excluding Goodwill)	15,756,000		15,756,000			15,756,000
Intangible Assets, Net (Including Goodwill)	169,380,000	173,489,000	169,380,000	$ 173,489,000	$ 169,905,000	171,118,000	$ 174,288,000	$ 119,710,000
Goodwill, Other Increase (Decrease)		$ (58,000)
Core Deposits [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Accumulated Amortization	4,671,000		4,671,000			2,933,000
Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Accumulated Amortization	$ 1,300,000		$ 1,300,000			$ 1,300,000