Loans, Credit Scores by Loan Class, Mortgage and Installment Segments (Details) - USD ($) $ in Thousands		3 Months Ended				6 Months Ended
		Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Loan ratings/credit scores by loan class [Abstract]
Accrued interest included in total		$ 9,138				$ 9,138		$ 8,538
Other Real Estate and Foreclosed Assets [Abstract]
Foreclosed residential real estate properties		1,200				1,200		1,200
Retail mortgage loans in process of foreclosure		600				600		300
Sale of Mortgage Loans [Abstract]
Proceeds from sale of mortgage loan						40,630	$ 16,460
Net gains on mortgage loans		4,302		$ 3,255		7,913	$ 5,826
Fixed Rate Residential Mortgage and Adjustable Rate Residential Mortgage [Member]
Sale of Mortgage Loans [Abstract]
Proceeds from sale of mortgage loan					$ 16,500
Net gains on mortgage loans					$ 50
Residential Adjustable Rate Mortgage Loans [Member]
Sale of Mortgage Loans [Abstract]
Proceeds from sale of mortgage loan			$ 40,600
Net gains on mortgage loans			10
Residential Fixed Rate Mortgage Loans [Member] | Freddie Mac [Member]
Sale of Mortgage Loans [Abstract]
Proceeds from sale of mortgage loan			29,800
Net gains on mortgage loans			$ 530
Mortgage [Member]
Loan ratings/credit scores by loan class [Abstract]
800 and above	[1]	140,753				140,753		121,012
750-799	[1]	492,544				492,544		476,484
700-749	[1]	254,575				254,575		252,126
650-699	[1]	114,571				114,571		114,460
600-649	[1]	39,140				39,140		41,748
550-599	[1]	20,801				20,801		17,301
500-549	[1]	13,490				13,490		9,789
Under 500	[1]	4,937				4,937		3,155
Unknown	[1]	10,048				10,048		10,912
Total	[1]	1,090,859				1,090,859		1,046,987
Accrued interest included in total	[1]	4,550				4,550		4,097
Mortgage [Member] | 1-4 Family [Member]
Loan ratings/credit scores by loan class [Abstract]
800 and above	[1]	110,599				110,599		94,492
750-799	[1]	391,241				391,241		384,344
700-749	[1]	195,867				195,867		202,440
650-699	[1]	89,819				89,819		91,847
600-649	[1]	31,668				31,668		34,342
550-599	[1]	16,755				16,755		13,771
500-549	[1]	11,333				11,333		8,439
Under 500	[1]	4,192				4,192		2,533
Unknown	[1]	8,186				8,186		8,236
Total	[1]	859,660				859,660		840,444
Accrued interest included in total	[1]	3,503				3,503		3,079
Mortgage [Member] | Resort Lending [Member]
Loan ratings/credit scores by loan class [Abstract]
800 and above	[1]	11,748				11,748		10,898
750-799	[1]	32,894				32,894		36,542
700-749	[1]	15,747				15,747		17,282
650-699	[1]	8,074				8,074		9,945
600-649	[1]	2,597				2,597		3,088
550-599	[1]	1,465				1,465		1,867
500-549	[1]	684				684		106
Under 500	[1]	81				81		143
Unknown	[1]	1,443				1,443		1,910
Total	[1]	74,733				74,733		81,781
Accrued interest included in total	[1]	367				367		363
Mortgage [Member] | Home Equity - 1st Lien [Member]
Loan ratings/credit scores by loan class [Abstract]
800 and above	[1]	5,783				5,783		6,784
750-799	[1]	15,624				15,624		17,303
700-749	[1]	9,584				9,584		9,155
650-699	[1]	3,623				3,623		3,987
600-649	[1]	663				663		959
550-599	[1]	652				652		427
500-549	[1]	325				325		418
Under 500	[1]	272				272		98
Unknown	[1]	0				0		113
Total	[1]	36,526				36,526		39,244
Accrued interest included in total	[1]	176				176		199
Mortgage [Member] | Home Equity - 2nd Lien [Member]
Loan ratings/credit scores by loan class [Abstract]
800 and above	[1]	12,623				12,623		8,838
750-799	[1]	52,785				52,785		38,295
700-749	[1]	33,377				33,377		23,249
650-699	[1]	13,055				13,055		8,681
600-649	[1]	4,212				4,212		3,359
550-599	[1]	1,929				1,929		1,236
500-549	[1]	1,148				1,148		826
Under 500	[1]	392				392		381
Unknown	[1]	419				419		653
Total	[1]	119,940				119,940		85,518
Accrued interest included in total	[1]	504				504		456
Installment [Member]
Loan ratings/credit scores by loan class [Abstract]
800 and above	[1]	56,161				56,161		48,026
750-799	[1]	238,533				238,533		208,972
700-749	[1]	96,428				96,428		87,978
650-699	[1]	29,423				29,423		28,162
600-649	[1]	8,323				8,323		7,668
550-599	[1]	3,460				3,460		3,360
500-549	[1]	2,056				2,056		1,775
Under 500	[1]	532				532		548
Unknown	[1]	10,525				10,525		9,690
Total	[1]	445,441				445,441		396,179
Accrued interest included in total	[1]	1,194				1,194		1,030
Installment [Member] | Home Equity - 1st Lien [Member]
Loan ratings/credit scores by loan class [Abstract]
800 and above	[1]	449				449		555
750-799	[1]	1,219				1,219		1,502
700-749	[1]	1,390				1,390		1,582
650-699	[1]	1,496				1,496		1,606
600-649	[1]	993				993		996
550-599	[1]	550				550		759
500-549	[1]	313				313		384
Under 500	[1]	19				19		51
Unknown	[1]	0				0		2
Total	[1]	6,429				6,429		7,437
Accrued interest included in total	[1]	23				23		28
Installment [Member] | Home Equity - 2nd Lien [Member]
Loan ratings/credit scores by loan class [Abstract]
800 and above	[1]	231				231		235
750-799	[1]	1,517				1,517		1,642
700-749	[1]	1,224				1,224		1,682
650-699	[1]	1,161				1,161		1,217
600-649	[1]	730				730		1,272
550-599	[1]	573				573		658
500-549	[1]	217				217		229
Under 500	[1]	55				55		6
Unknown	[1]	43				43		103
Total	[1]	5,751				5,751		7,044
Accrued interest included in total	[1]	19				19		25
Installment [Member] | Boat Lending [Member]
Loan ratings/credit scores by loan class [Abstract]
800 and above	[1]	26,585				26,585		20,767
750-799	[1]	115,402				115,402		100,191
700-749	[1]	41,608				41,608		35,455
650-699	[1]	10,612				10,612		10,581
600-649	[1]	1,879				1,879		1,657
550-599	[1]	831				831		652
500-549	[1]	486				486		286
Under 500	[1]	229				229		266
Unknown	[1]	26				26		39
Total	[1]	197,658				197,658		169,894
Accrued interest included in total	[1]	493				493		403
Installment [Member] | Recreational Vehicle Lending [Member]
Loan ratings/credit scores by loan class [Abstract]
800 and above	[1]	22,213				22,213		20,197
750-799	[1]	85,635				85,635		74,154
700-749	[1]	28,261				28,261		24,890
650-699	[1]	5,728				5,728		4,918
600-649	[1]	1,767				1,767		992
550-599	[1]	653				653		453
500-549	[1]	181				181		225
Under 500	[1]	42				42		7
Unknown	[1]	0				0		0
Total	[1]	144,480				144,480		125,836
Accrued interest included in total	[1]	368				368		311
Installment [Member] | Other [Member]
Loan ratings/credit scores by loan class [Abstract]
800 and above	[1]	6,683				6,683		6,272
750-799	[1]	34,760				34,760		31,483
700-749	[1]	23,945				23,945		24,369
650-699	[1]	10,426				10,426		9,840
600-649	[1]	2,954				2,954		2,751
550-599	[1]	853				853		838
500-549	[1]	859				859		651
Under 500	[1]	187				187		218
Unknown	[1]	10,456				10,456		9,546
Total	[1]	91,123				91,123		85,968
Accrued interest included in total	[1]	$ 291				$ 291		$ 263

[1] Credit scores have been updated within the last twelve months.