Goodwill and other intangibles (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 159,595,000	$ 112,739,000	$ 159,595,000	$ 112,739,000
Other Intangible Assets, Net	10,917,000	6,682,000	11,523,000	6,971,000
Goodwill, Acquired During Period	0	0	46,856,000
Indefinite-lived Intangible Assets Acquired	0	0
Acquired goodwill and intangibles	0	0
Amortization of Intangible Assets	606,000	289,000
Finite-lived Intangible Assets Acquired	14,456,000		14,456,000
Indefinite-lived Intangible Assets Acquired	1,300,000		1,300,000
Finite-Lived Intangible Assets, Accumulated Amortization	4,839,000		4,233,000
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	1,657,000
Finite-Lived Intangible Assets, Amortization Expense, Year Two	1,798,000
Finite-Lived Intangible Assets, Amortization Expense, Year Three	1,487,000
Finite-Lived Intangible Assets, Amortization Expense, Year Four	1,323,000
Finite-Lived Intangible Assets, Amortization Expense, Year Five	1,215,000
Intangible Assets, Gross (Excluding Goodwill)	15,756,000		15,756,000
Intangible Assets, Net (Including Goodwill)	170,512,000	$ 119,421,000	171,118,000	$ 119,710,000
Core Deposits [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Accumulated Amortization	3,539,000		2,933,000
Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Accumulated Amortization	$ 1,300,000		$ 1,300,000