Loans, Impaired Financing Receivables (Q3) (Details) - USD ($) $ in Thousands		3 Months Ended				9 Months Ended				12 Months Ended
		Sep. 30, 2017		Sep. 30, 2016	[3]	Sep. 30, 2017		Sep. 30, 2016	[4]	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014	[5]
Impaired loan with no allocated allowance [Abstract]
TDR		$ 349				$ 349				$ 1,782		$ 2,518
Non - TDR		186				186				1,107		203
Impaired loans with an allocated allowance [Abstract]
TDR - allowance based on collateral		2,320				2,320				3,527		4,810
TDR - allowance based on present value cash flow		65,449				65,449				72,613		81,002
Non - TDR - allowance based on collateral		202				202				491		260
Total impaired loans		68,506				68,506				79,520		88,793
Amount of allowance for loan losses allocated [Abstract]
TDR - allowance based on collateral		641				641				1,868		2,436
TDR - allowance based on present value cash flow		6,329				6,329				7,146		8,471
Non - TDR - allowance based on collateral		91				91				138		76
Total amount of allowance for loan losses allocated		7,061				7,061				9,152		10,983
Impaired Loans by class [Abstract]
Recorded Investment, with no related allowance		538	[1]			538	[1]			2,891	[1],[2]	2,727	[2]
Unpaid Principal Balance, with no related allowance		1,100	[1]			1,100	[1]			5,191	[1],[2]	3,744	[2]
No Related Allowance		0	[1]			0	[1]			0	[1],[2]	0	[2]
Recorded Investment, with an allowance recorded		68,256	[1]			68,256	[1]			76,940	[1],[2]	86,404	[2]
Unpaid Principal Balance, with an allowance recorded		70,334	[1]			70,334	[1]			79,520	[1],[2]	90,182	[2]
Recorded Investment		68,794	[1]			68,794	[1]			79,831	[1],[2]	89,131	[2]
Unpaid Principal Balance		71,434	[1]			71,434	[1]			84,711	[1],[2]	93,926	[2]
Related Allowance		7,061	[1]			7,061	[1]			9,152	[1],[2]	10,983	[2]
Accrued interest included in recorded investment		288	[1]			288	[1]			311	[1],[2]	338	[2]
Average recorded investment in and interest income earned on impaired loans by class [Abstract]
Average Recorded Investment, with No Related Allowance		573	[3]	$ 696		1,103	[4]	$ 1,669		1,913	[5]	7,628	[5]	$ 12,225
Interest Income Recognized, with No Related Allowance		17	[3]	6		37	[4]	43		84	[5]	739	[5]	469
Average Recorded Investment, with Related Allowance		69,775	[3]	83,676		72,397	[4]	84,839		83,258	[5]	97,018	[5]	107,692
Interest Income Recognized, with Related Allowance		810	[3]	902		2,524	[4]	2,710		3,552	[5]	3,835	[5]	4,565
Average Recorded Investment		70,348	[3]	84,372		73,500	[4]	86,508		85,171	[5]	104,646	[5]	119,917
Interest Income Recognized		827	[3]	908		2,561	[4]	2,753		3,636	[5]	4,574	[5]	5,034
Commercial [Member] | Income Producing - Real Estate [Member]
Impaired Loans by class [Abstract]
Recorded Investment, with no related allowance		0	[1]			0	[1]			517	[1],[2]	641	[2]
Unpaid Principal Balance, with no related allowance		0	[1]			0	[1]			768	[1],[2]	851	[2]
No Related Allowance		0	[1]			0	[1]			0	[1],[2]	0	[2]
Recorded Investment, with an allowance recorded		6,975	[1]			6,975	[1]			7,737	[1],[2]	8,377	[2]
Unpaid Principal Balance, with an allowance recorded		7,121	[1]			7,121	[1]			7,880	[1],[2]	9,232	[2]
Recorded Investment		6,975	[1]			6,975	[1]			8,254	[1],[2]	9,018	[2]
Unpaid Principal Balance		7,121	[1]			7,121	[1]			8,648	[1],[2]	10,083	[2]
Related Allowance		482	[1]			482	[1]			554	[1],[2]	516	[2]
Average recorded investment in and interest income earned on impaired loans by class [Abstract]
Average Recorded Investment, with No Related Allowance		0	[3]	551		222	[4]	632		609	[5]	4,520	[5]	7,660
Interest Income Recognized, with No Related Allowance		0	[3]	0		0	[4]	2		2	[5]	387	[5]	250
Average Recorded Investment, with Related Allowance		7,311	[3]	8,000		7,525	[4]	8,153		8,069	[5]	12,677	[5]	12,772
Interest Income Recognized, with Related Allowance		91	[3]	111		300	[4]	318		427	[5]	439	[5]	677
Average Recorded Investment		7,311	[3]	8,551		7,747	[4]	8,785		8,678	[5]	17,197	[5]	20,432
Interest Income Recognized		91	[3]	111		300	[4]	320		429	[5]	826	[5]	927
Commercial [Member] | Land, Land Development and Construction - Real Estate [Member]
Impaired Loans by class [Abstract]
Recorded Investment, with no related allowance		0	[1]			0	[1]			31	[1],[2]	818	[2]
Unpaid Principal Balance, with no related allowance		0	[1]			0	[1]			709	[1],[2]	1,393	[2]
No Related Allowance		0	[1]			0	[1]			0	[1],[2]	0	[2]
Recorded Investment, with an allowance recorded		169	[1]			169	[1]			239	[1],[2]	1,690	[2]
Unpaid Principal Balance, with an allowance recorded		197	[1]			197	[1]			244	[1],[2]	1,778	[2]
Recorded Investment		169	[1]			169	[1]			270	[1],[2]	2,508	[2]
Unpaid Principal Balance		197	[1]			197	[1]			953	[1],[2]	3,171	[2]
Related Allowance		10	[1]			10	[1]			36	[1],[2]	296	[2]
Average recorded investment in and interest income earned on impaired loans by class [Abstract]
Average Recorded Investment, with No Related Allowance		0	[3]	133		8	[4]	405		330	[5]	952	[5]	1,145
Interest Income Recognized, with No Related Allowance		0	[3]	0		0	[4]	7		7	[5]	79	[5]	64
Average Recorded Investment, with Related Allowance		171	[3]	1,117		187	[4]	1,352		1,129	[5]	2,219	[5]	3,939
Interest Income Recognized, with Related Allowance		2	[3]	3		6	[4]	29		31	[5]	54	[5]	149
Average Recorded Investment		171	[3]	1,250		195	[4]	1,757		1,459	[5]	3,171	[5]	5,084
Interest Income Recognized		2	[3]	3		6	[4]	36		38	[5]	133	[5]	213
Commercial [Member] | Commercial and Industrial [Member]
Impaired Loans by class [Abstract]
Recorded Investment, with no related allowance		535	[1]			535	[1]			2,341	[1],[2]	1,245	[2]
Unpaid Principal Balance, with no related allowance		557	[1]			557	[1]			3,261	[1],[2]	1,241	[2]
No Related Allowance		0	[1]			0	[1]			0	[1],[2]	0	[2]
Recorded Investment, with an allowance recorded		2,578	[1]			2,578	[1]			4,902	[1],[2]	4,097	[2]
Unpaid Principal Balance, with an allowance recorded		2,612	[1]			2,612	[1]			5,246	[1],[2]	4,439	[2]
Recorded Investment		3,113	[1]			3,113	[1]			7,243	[1],[2]	5,342	[2]
Unpaid Principal Balance		3,169	[1]			3,169	[1]			8,507	[1],[2]	5,680	[2]
Related Allowance		475	[1]			475	[1]			1,654	[1],[2]	1,896	[2]
Average recorded investment in and interest income earned on impaired loans by class [Abstract]
Average Recorded Investment, with No Related Allowance		445	[3]	0		808	[4]	616		961	[5]	2,125	[5]	3,351
Interest Income Recognized, with No Related Allowance		8	[3]	0		16	[4]	21		54	[5]	257	[5]	152
Average Recorded Investment, with Related Allowance		2,878	[3]	7,145		3,488	[4]	5,929		5,723	[5]	6,663	[5]	8,500
Interest Income Recognized, with Related Allowance		26	[3]	69		98	[4]	151		189	[5]	104	[5]	294
Average Recorded Investment		3,323	[3]	7,145		4,296	[4]	6,545		6,684	[5]	8,788	[5]	11,851
Interest Income Recognized		34	[3]	69		114	[4]	172		243	[5]	361	[5]	446
Mortgage [Member] | 1-4 Family [Member]
Impaired Loans by class [Abstract]
Recorded Investment, with no related allowance		2	[1]			2	[1]			2	[1],[2]	23	[2]
Unpaid Principal Balance, with no related allowance		472	[1]			472	[1]			387	[1],[2]	183	[2]
No Related Allowance		0	[1]			0	[1]			0	[1],[2]	0	[2]
Recorded Investment, with an allowance recorded		37,872	[1]			37,872	[1]			41,701	[1],[2]	47,792	[2]
Unpaid Principal Balance, with an allowance recorded		39,393	[1]			39,393	[1]			43,479	[1],[2]	49,808	[2]
Recorded Investment		37,874	[1]			37,874	[1]			41,703	[1],[2]	47,815	[2]
Unpaid Principal Balance		39,865	[1]			39,865	[1]			43,866	[1],[2]	49,991	[2]
Related Allowance		3,517	[1]			3,517	[1]			4,100	[1],[2]	5,132	[2]
Average recorded investment in and interest income earned on impaired loans by class [Abstract]
Average Recorded Investment, with No Related Allowance		127	[3]	12		64	[4]	12		10	[5]	19	[5]	29
Interest Income Recognized, with No Related Allowance		7	[3]	3		16	[4]	9		16	[5]	11	[5]	0
Average Recorded Investment, with Related Allowance		38,533	[3]	44,256		39,716	[4]	45,728		44,923	[5]	50,421	[5]	55,877
Interest Income Recognized, with Related Allowance		462	[3]	470		1,420	[4]	1,447		1,918	[5]	2,140	[5]	2,286
Average Recorded Investment		38,660	[3]	44,268		39,780	[4]	45,740		44,933	[5]	50,440	[5]	55,906
Interest Income Recognized		469	[3]	473		1,436	[4]	1,456		1,934	[5]	2,151	[5]	2,286
Mortgage [Member] | Resort Lending [Member]
Impaired Loans by class [Abstract]
Recorded Investment, with no related allowance		0	[1]			0	[1]			0	[1],[2]	0	[2]
Unpaid Principal Balance, with no related allowance		0	[1]			0	[1]			0	[1],[2]	0	[2]
No Related Allowance		0	[1]			0	[1]			0	[1],[2]	0	[2]
Recorded Investment, with an allowance recorded		16,098	[1]			16,098	[1]			16,898	[1],[2]	18,148	[2]
Unpaid Principal Balance, with an allowance recorded		16,169	[1]			16,169	[1]			16,931	[1],[2]	18,319	[2]
Recorded Investment		16,098	[1]			16,098	[1]			16,898	[1],[2]	18,148	[2]
Unpaid Principal Balance		16,169	[1]			16,169	[1]			16,931	[1],[2]	18,319	[2]
Related Allowance		2,264	[1]			2,264	[1]			2,453	[1],[2]	2,662	[2]
Average recorded investment in and interest income earned on impaired loans by class [Abstract]
Average Recorded Investment, with No Related Allowance		0	[3]	0		0	[4]	0		0	[5]	12	[5]	40
Interest Income Recognized, with No Related Allowance		0	[3]	0		0	[4]	0		0	[5]	0	[5]	1
Average Recorded Investment, with Related Allowance		16,175	[3]	17,372		16,485	[4]	17,705		17,544	[5]	18,448	[5]	19,458
Interest Income Recognized, with Related Allowance		153	[3]	161		464	[4]	480		619	[5]	670	[5]	753
Average Recorded Investment		16,175	[3]	17,372		16,485	[4]	17,705		17,544	[5]	18,460	[5]	19,498
Interest Income Recognized		153	[3]	161		464	[4]	480		619	[5]	670	[5]	754
Mortgage [Member] | Home Equity - 1st Lien [Member]
Impaired Loans by class [Abstract]
Recorded Investment, with no related allowance		0	[1]			0	[1]			0	[1],[2]	0	[2]
Unpaid Principal Balance, with no related allowance		0	[1]			0	[1]			0	[1],[2]	0	[2]
No Related Allowance		0	[1]			0	[1]			0	[1],[2]	0	[2]
Recorded Investment, with an allowance recorded		171	[1]			171	[1]			235	[1],[2]	168	[2]
Unpaid Principal Balance, with an allowance recorded		238	[1]			238	[1]			242	[1],[2]	172	[2]
Recorded Investment		171	[1]			171	[1]			235	[1],[2]	168	[2]
Unpaid Principal Balance		238	[1]			238	[1]			242	[1],[2]	172	[2]
Related Allowance		30	[1]			30	[1]			10	[1],[2]	9	[2]
Average recorded investment in and interest income earned on impaired loans by class [Abstract]
Average Recorded Investment, with No Related Allowance		0	[3]	0		0	[4]	0		0	[5]	0	[5]	0
Interest Income Recognized, with No Related Allowance		0	[3]	0		0	[4]	0		0	[5]	0	[5]	0
Average Recorded Investment, with Related Allowance		201	[3]	241		218	[4]	223		226	[5]	161	[5]	160
Interest Income Recognized, with Related Allowance		1	[3]	2		5	[4]	6		10	[5]	8	[5]	6
Average Recorded Investment		201	[3]	241		218	[4]	223		226	[5]	161	[5]	160
Interest Income Recognized		1	[3]	2		5	[4]	6		10	[5]	8	[5]	6
Mortgage [Member] | Home Equity - 2nd Lien [Member]
Impaired Loans by class [Abstract]
Recorded Investment, with no related allowance		0	[1]			0	[1]			0	[1],[2]	0	[2]
Unpaid Principal Balance, with no related allowance		0	[1]			0	[1]			0	[1],[2]	0	[2]
No Related Allowance		0	[1]			0	[1]			0	[1],[2]	0	[2]
Recorded Investment, with an allowance recorded		179	[1]			179	[1]			315	[1],[2]	244	[2]
Unpaid Principal Balance, with an allowance recorded		213	[1]			213	[1]			398	[1],[2]	325	[2]
Recorded Investment		179	[1]			179	[1]			315	[1],[2]	244	[2]
Unpaid Principal Balance		213	[1]			213	[1]			398	[1],[2]	325	[2]
Related Allowance		12	[1]			12	[1]			16	[1],[2]	15	[2]
Average recorded investment in and interest income earned on impaired loans by class [Abstract]
Average Recorded Investment, with No Related Allowance		0	[3]	0		0	[4]	0		0	[5]	0	[5]	0
Interest Income Recognized, with No Related Allowance		0	[3]	0		0	[4]	0		0	[5]	0	[5]	0
Average Recorded Investment, with Related Allowance		180	[3]	280		217	[4]	231		248	[5]	172	[5]	57
Interest Income Recognized, with Related Allowance		2	[3]	6		5	[4]	11		14	[5]	13	[5]	2
Average Recorded Investment		180	[3]	280		217	[4]	231		248	[5]	172	[5]	57
Interest Income Recognized		2	[3]	6		5	[4]	11		14	[5]	13	[5]	2
Installment [Member] | Home Equity - 1st Lien [Member]
Impaired Loans by class [Abstract]
Recorded Investment, with no related allowance		1	[1]			1	[1]			0	[1],[2]	0	[2]
Unpaid Principal Balance, with no related allowance		71	[1]			71	[1]			66	[1],[2]	76	[2]
No Related Allowance		0	[1]			0	[1]			0	[1],[2]	0	[2]
Recorded Investment, with an allowance recorded		1,791	[1]			1,791	[1]			1,994	[1],[2]	2,364	[2]
Unpaid Principal Balance, with an allowance recorded		1,921	[1]			1,921	[1]			2,117	[1],[2]	2,492	[2]
Recorded Investment		1,792	[1]			1,792	[1]			1,994	[1],[2]	2,364	[2]
Unpaid Principal Balance		1,992	[1]			1,992	[1]			2,183	[1],[2]	2,568	[2]
Related Allowance		85	[1]			85	[1]			118	[1],[2]	143	[2]
Average recorded investment in and interest income earned on impaired loans by class [Abstract]
Average Recorded Investment, with No Related Allowance		1	[3]	0		1	[4]	0		0	[5]	0	[5]	0
Interest Income Recognized, with No Related Allowance		1	[3]	3		4	[4]	4		5	[5]	5	[5]	2
Average Recorded Investment, with Related Allowance		1,808	[3]	2,140		1,874	[4]	2,233		2,185	[5]	2,539	[5]	2,837
Interest Income Recognized, with Related Allowance		40	[3]	34		107	[4]	118		147	[5]	176	[5]	174
Average Recorded Investment		1,809	[3]	2,140		1,875	[4]	2,233		2,185	[5]	2,539	[5]	2,837
Interest Income Recognized		41	[3]	37		111	[4]	122		152	[5]	181	[5]	176
Installment [Member] | Home Equity - 2nd Lien [Member]
Impaired Loans by class [Abstract]
Recorded Investment, with no related allowance		0	[1]			0	[1]			0	[1],[2]	0	[2]
Unpaid Principal Balance, with no related allowance		0	[1]			0	[1]			0	[1],[2]	0	[2]
No Related Allowance		0	[1]			0	[1]			0	[1],[2]	0	[2]
Recorded Investment, with an allowance recorded		1,969	[1]			1,969	[1]			2,415	[1],[2]	2,929	[2]
Unpaid Principal Balance, with an allowance recorded		1,994	[1]			1,994	[1]			2,443	[1],[2]	2,951	[2]
Recorded Investment		1,969	[1]			1,969	[1]			2,415	[1],[2]	2,929	[2]
Unpaid Principal Balance		1,994	[1]			1,994	[1]			2,443	[1],[2]	2,951	[2]
Related Allowance		161	[1]			161	[1]			182	[1],[2]	271	[2]
Average recorded investment in and interest income earned on impaired loans by class [Abstract]
Average Recorded Investment, with No Related Allowance		0	[3]	0		0	[4]	4		3	[5]	0	[5]	0
Interest Income Recognized, with No Related Allowance		0	[3]	0		0	[4]	0		0	[5]	0	[5]	0
Average Recorded Investment, with Related Allowance		2,058	[3]	2,585		2,210	[4]	2,723		2,661	[5]	3,055	[5]	3,359
Interest Income Recognized, with Related Allowance		26	[3]	37		96	[4]	122		162	[5]	193	[5]	188
Average Recorded Investment		2,058	[3]	2,585		2,210	[4]	2,727		2,664	[5]	3,055	[5]	3,359
Interest Income Recognized		26	[3]	37		96	[4]	122		162	[5]	$ 193	[5]	$ 188
Installment [Member] | Boat Lending [Member]
Impaired Loans by class [Abstract]
Recorded Investment, with no related allowance	[1]	0				0				0
Unpaid Principal Balance, with no related allowance	[1]	0				0				0
No Related Allowance	[1]	0				0				0
Recorded Investment, with an allowance recorded	[1]	1				1				1
Unpaid Principal Balance, with an allowance recorded	[1]	6				6				6
Recorded Investment	[1]	1				1				1
Unpaid Principal Balance	[1]	6				6				6
Related Allowance	[1]	1				1				0
Average recorded investment in and interest income earned on impaired loans by class [Abstract]
Average Recorded Investment, with No Related Allowance		0	[3]	0		0	[4]	0
Interest Income Recognized, with No Related Allowance		0	[3]	0		0	[4]	0
Average Recorded Investment, with Related Allowance		1	[3]	2		1	[4]	2
Interest Income Recognized, with Related Allowance		0	[3]	0		0	[4]	0
Average Recorded Investment		1	[3]	2		1	[4]	2
Interest Income Recognized		0	[3]	0		0	[4]	0
Installment [Member] | Recreational Vehicle Lending [Member]
Impaired Loans by class [Abstract]
Recorded Investment, with no related allowance	[1]	0				0				0
Unpaid Principal Balance, with no related allowance	[1]	0				0				0
No Related Allowance	[1]	0				0				0
Recorded Investment, with an allowance recorded	[1]	93				93				109
Unpaid Principal Balance, with an allowance recorded	[1]	93				93				108
Recorded Investment	[1]	93				93				109
Unpaid Principal Balance	[1]	93				93				108
Related Allowance	[1]	5				5				6
Average recorded investment in and interest income earned on impaired loans by class [Abstract]
Average Recorded Investment, with No Related Allowance		0	[3]	0		0	[4]	0
Interest Income Recognized, with No Related Allowance		0	[3]	0		0	[4]	0
Average Recorded Investment, with Related Allowance		98	[3]	114		103	[4]	117
Interest Income Recognized, with Related Allowance		1	[3]	2		4	[4]	5
Average Recorded Investment		98	[3]	114		103	[4]	117
Interest Income Recognized		1	[3]	2		4	[4]	5
Installment [Member] | Other [Member]
Impaired Loans by class [Abstract]
Recorded Investment, with no related allowance	[1]	0				0				0
Unpaid Principal Balance, with no related allowance	[1]	0				0				0
No Related Allowance	[1]	0				0				0
Recorded Investment, with an allowance recorded	[1]	360				360				394
Unpaid Principal Balance, with an allowance recorded	[1]	377				377				426
Recorded Investment	[1]	360				360				394
Unpaid Principal Balance	[1]	377				377				426
Related Allowance	[1]	19				19				$ 23
Average recorded investment in and interest income earned on impaired loans by class [Abstract]
Average Recorded Investment, with No Related Allowance		0	[3]	0		0	[4]	0
Interest Income Recognized, with No Related Allowance		1	[3]	0		1	[4]	0
Average Recorded Investment, with Related Allowance		361	[3]	424		373	[4]	443
Interest Income Recognized, with Related Allowance		6	[3]	7		19	[4]	23
Average Recorded Investment		361	[3]	424		373	[4]	443
Interest Income Recognized		$ 7	[3]	$ 7		$ 20	[4]	$ 23

[1] There were no impaired purchased mortgage loans at September 30, 2017 or December 31, 2016.

[2] There were no impaired payment plan receivables or purchased mortgage loans at December 31, 2016 or 2015.

[3] There were no impaired purchased mortgage loans during the three month periods ended September 30, 2017 and 2016, respectively.

[4] There were no impaired purchased mortgage loans during the nine month periods ended September 30, 2017 and 2016, respectively.

[5] There were no impaired payment plan receivables or purchased mortgage loans during the years ending December 31, 2016, 2015 and 2014.