Goodwill and Other Intangible Assets, Summary of Core Deposit and Other Intangibles (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Summary of core deposit intangibles and other intangibles
Other intangible amortization	$ 2,253	$ 2,686	$ 7,939	$ 7,237
Core Deposit Intangibles
Summary of core deposit intangibles and other intangibles
Gross carrying amount at the beginning of the year					$ 80,730	$ 58,100
Additions during the period			7,379		22,630
Accumulated amortization	(19,003)		(19,003)		(12,456)
Net book value	69,107		69,107		68,274
Other intangible amortization			6,547		7,130
Other Intangibles
Summary of core deposit intangibles and other intangibles
Gross carrying amount at the beginning of the year					38,970	$ 44,887
Additions during the period			200		0
Reductions due to sale			(19,000)
Accumulated amortization	(20,335)		(20,335)		(24,643)
Net book value	$ 1,400		1,400		20,027
Other intangible amortization			1,393		2,818
Other Intangibles | Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member]
Summary of core deposit intangibles and other intangibles
Reductions due to sale			$ (17,435)		$ (217)