Goodwill and other intangibles (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 159,595,000	$ 158,057,000	$ 159,595,000	$ 158,057,000	$ 159,595,000	$ 159,595,000	$ 112,739,000	$ 112,739,000
Other Intangible Assets, Net	10,310,000	16,231,000	10,310,000	16,231,000	10,917,000	11,523,000	6,682,000	6,971,000
Goodwill, Acquired During Period	0	45,318,000	0	45,318,000
Indefinite-lived Intangible Assets Acquired	0	10,251,000	0	10,251,000
Acquired goodwill and intangibles	0	55,569,000	0	55,569,000
Amortization of Intangible Assets	607,000	702,000	1,213,000	991,000
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	5,446,000		5,446,000			4,233,000
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	1,050,000		1,050,000
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)	169,905,000	$ 174,288,000	169,905,000	$ 174,288,000	$ 170,512,000	171,118,000	$ 119,421,000	$ 119,710,000
Core Deposits [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Accumulated Amortization	4,146,000		4,146,000			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