Goodwill and other intangibles (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 157,999	$ 112,739	$ 157,999	$ 112,739	$ 112,739	$ 72,334
Other Intangible Assets, Net	15,490	7,260	15,490	7,260	6,971	0
Goodwill, Acquired During Period			45,260	40,405	40,405
Indefinite-lived Intangible Assets Acquired			10,251	7,549
Acquired goodwill and intangibles			55,511	47,954
Amortization of Intangible Assets	741	289	1,732	289
Finite-lived Intangible Assets Acquired	16,500		16,500		6,249
Indefinite-lived Intangible Assets Acquired	1,300		1,300		1,300
Finite-Lived Intangible Assets, Accumulated Amortization	2,310		2,310		578
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	741		741
Finite-Lived Intangible Assets, Amortization Expense, Year Two	2,502		2,502
Finite-Lived Intangible Assets, Amortization Expense, Year Three	2,040		2,040
Finite-Lived Intangible Assets, Amortization Expense, Year Four	1,725		1,725
Finite-Lived Intangible Assets, Amortization Expense, Year Five	1,548		1,548
Intangible Assets, Gross (Excluding Goodwill)	17,800		17,800		7,549
Intangible Assets, Net (Including Goodwill)	173,489	$ 119,999	173,489	$ 119,999	119,710	$ 72,334
Core Deposits [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Accumulated Amortization	2,310		2,310		578
Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Accumulated Amortization	$ 0		$ 0		$ 0