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Amount of credit loss expense (reversal of expense) for financing receivable.

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Loans (Allowance for Credit Losses) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Allowance for Credit Losses [Roll Forward]
Beginning Balance	$ 42,431	$ 16,239	$ 16,278	$ 15,823
Provision for credit loss expense	4,500	2,800	15,550	3,725
Initial allowance on loans purchased with credit deterioration			0
Loans charged-off	(322)	(3,284)	(1,090)	(4,083)
Recoveries collected	159	114	377	404
Ending Balance	46,768	15,869	46,768	15,869
Impact of adopting ASC 326 - PCD Loans
Allowance for Credit Losses [Roll Forward]
Beginning Balance			405
Impact of ASC 326 Adoption \| Impact of adopting ASC 326
Allowance for Credit Losses [Roll Forward]
Beginning Balance			8,767
Impact of ASC 326 Adoption \| Impact of adopting ASC 326 - PCD Loans
Allowance for Credit Losses [Roll Forward]
Beginning Balance			6,886
Commercial and Industrial Loans
Allowance for Credit Losses [Roll Forward]
Beginning Balance	8,787		4,799
Provision for credit loss expense	(1,017)		(1,182)
Initial allowance on loans purchased with credit deterioration			0
Loans charged-off	(73)		(369)
Recoveries collected	3		16
Ending Balance	7,700		7,700
Commercial and Industrial Loans \| Impact of ASC 326 Adoption \| Impact of adopting ASC 326
Allowance for Credit Losses [Roll Forward]
Beginning Balance			2,245
Commercial and Industrial Loans \| Impact of ASC 326 Adoption \| Impact of adopting ASC 326 - PCD Loans
Allowance for Credit Losses [Roll Forward]
Beginning Balance			2,191
Commercial Real Estate Loans
Allowance for Credit Losses [Roll Forward]
Beginning Balance	22,369	5,841	4,692	5,291
Provision for credit loss expense	5,931	(1,410)	16,145	(741)
Initial allowance on loans purchased with credit deterioration			0
Loans charged-off	(9)	(136)	(9)	(274)
Recoveries collected	91	5	106	24
Ending Balance	28,382	4,300	28,382	4,300
Commercial Real Estate Loans \| Impact of adopting ASC 326 - PCD Loans
Allowance for Credit Losses [Roll Forward]
Beginning Balance			400
Commercial Real Estate Loans \| Impact of ASC 326 Adoption \| Impact of adopting ASC 326
Allowance for Credit Losses [Roll Forward]
Beginning Balance			3,063
Commercial Real Estate Loans \| Impact of ASC 326 Adoption \| Impact of adopting ASC 326 - PCD Loans
Allowance for Credit Losses [Roll Forward]
Beginning Balance			4,385
Agricultural Loans
Allowance for Credit Losses [Roll Forward]
Beginning Balance	7,030	5,725	5,315	5,776
Provision for credit loss expense	(315)	(373)	(166)	(424)
Initial allowance on loans purchased with credit deterioration			0
Loans charged-off	0	0	0	0
Recoveries collected	0	0	0	0
Ending Balance	6,715	5,352	6,715	5,352
Agricultural Loans \| Impact of adopting ASC 326 - PCD Loans
Allowance for Credit Losses [Roll Forward]
Beginning Balance			0
Agricultural Loans \| Impact of ASC 326 Adoption \| Impact of adopting ASC 326
Allowance for Credit Losses [Roll Forward]
Beginning Balance			1,438
Agricultural Loans \| Impact of ASC 326 Adoption \| Impact of adopting ASC 326 - PCD Loans
Allowance for Credit Losses [Roll Forward]
Beginning Balance			128
Leases
Allowance for Credit Losses [Roll Forward]
Beginning Balance	202		0
Provision for credit loss expense	4		101
Initial allowance on loans purchased with credit deterioration			0
Loans charged-off	0		0
Recoveries collected	0		0
Ending Balance	206		206
Leases \| Impact of ASC 326 Adoption \| Impact of adopting ASC 326
Allowance for Credit Losses [Roll Forward]
Beginning Balance			105
Leases \| Impact of ASC 326 Adoption \| Impact of adopting ASC 326 - PCD Loans
Allowance for Credit Losses [Roll Forward]
Beginning Balance			0
Consumer Loans
Allowance for Credit Losses [Roll Forward]
Beginning Balance	496	422	434	420
Provision for credit loss expense	70	174	385	507
Initial allowance on loans purchased with credit deterioration			0
Loans charged-off	(138)	(277)	(520)	(822)
Recoveries collected	64	99	252	313
Ending Balance	492	418	492	418
Consumer Loans \| Impact of adopting ASC 326 - PCD Loans
Allowance for Credit Losses [Roll Forward]
Beginning Balance			0
Consumer Loans \| Impact of ASC 326 Adoption \| Impact of adopting ASC 326
Allowance for Credit Losses [Roll Forward]
Beginning Balance			(59)
Consumer Loans \| Impact of ASC 326 Adoption \| Impact of adopting ASC 326 - PCD Loans
Allowance for Credit Losses [Roll Forward]
Beginning Balance			0
Home Equity Loans
Allowance for Credit Losses [Roll Forward]
Beginning Balance	1,062	258	200	229
Provision for credit loss expense	0	(72)	65	(33)
Initial allowance on loans purchased with credit deterioration			0
Loans charged-off	(67)	0	(67)	(10)
Recoveries collected	0	8	0	8
Ending Balance	995	194	995	194
Home Equity Loans \| Impact of adopting ASC 326 - PCD Loans
Allowance for Credit Losses [Roll Forward]
Beginning Balance			0
Home Equity Loans \| Impact of ASC 326 Adoption \| Impact of adopting ASC 326
Allowance for Credit Losses [Roll Forward]
Beginning Balance			762
Home Equity Loans \| Impact of ASC 326 Adoption \| Impact of adopting ASC 326 - PCD Loans
Allowance for Credit Losses [Roll Forward]
Beginning Balance			35
Credit Cards
Allowance for Credit Losses [Roll Forward]
Beginning Balance	125		0
Provision for credit loss expense	39		98
Initial allowance on loans purchased with credit deterioration			0
Loans charged-off	(27)		(86)
Recoveries collected	0		1
Ending Balance	137		137
Credit Cards \| Impact of ASC 326 Adoption \| Impact of adopting ASC 326
Allowance for Credit Losses [Roll Forward]
Beginning Balance			124
Credit Cards \| Impact of ASC 326 Adoption \| Impact of adopting ASC 326 - PCD Loans
Allowance for Credit Losses [Roll Forward]
Beginning Balance			0
Residential Mortgage Loans
Allowance for Credit Losses [Roll Forward]
Beginning Balance	2,360	349	333	472
Provision for credit loss expense	(212)	25	104	(54)
Initial allowance on loans purchased with credit deterioration			0
Loans charged-off	(8)	(12)	(39)	(62)
Recoveries collected	1	0	2	6
Ending Balance	2,141	362	2,141	362
Residential Mortgage Loans \| Impact of adopting ASC 326 - PCD Loans
Allowance for Credit Losses [Roll Forward]
Beginning Balance			5
Residential Mortgage Loans \| Impact of ASC 326 Adoption \| Impact of adopting ASC 326
Allowance for Credit Losses [Roll Forward]
Beginning Balance			1,594
Residential Mortgage Loans \| Impact of ASC 326 Adoption \| Impact of adopting ASC 326 - PCD Loans
Allowance for Credit Losses [Roll Forward]
Beginning Balance			147
Unallocated
Allowance for Credit Losses [Roll Forward]
Beginning Balance	0	652	505	682
Provision for credit loss expense	0	(12)	0	(42)
Initial allowance on loans purchased with credit deterioration			0
Loans charged-off	0	0	0	0
Recoveries collected	0	0	0	0
Ending Balance	$ 0	$ 640	0	$ 640
Unallocated \| Impact of adopting ASC 326 - PCD Loans
Allowance for Credit Losses [Roll Forward]
Beginning Balance			0
Unallocated \| Impact of ASC 326 Adoption \| Impact of adopting ASC 326
Allowance for Credit Losses [Roll Forward]
Beginning Balance			(505)
Unallocated \| Impact of ASC 326 Adoption \| Impact of adopting ASC 326 - PCD Loans
Allowance for Credit Losses [Roll Forward]
Beginning Balance			$ 0