Loans - Impaired Loans - Average Recorded Investment and Interest Income Recognized (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Average Recorded Investment
With no related allowance recorded	$ 20,982	$ 27,868	$ 35,043
With an allowance recorded	605	518	6,185
Total impaired loans	21,587	28,386	41,228
Interest Income Recognized
With no related allowance recorded	323	303	467
With an allowance recorded		3	1
Total impaired loans	323	306	468
Commercial
Average Recorded Investment
With no related allowance recorded	238	785	764
With an allowance recorded	2	2
Real estate - commercial | Owner occupied general purpose
Average Recorded Investment
With no related allowance recorded	2,097	4,720	4,834
With an allowance recorded			365
Interest Income Recognized
With no related allowance recorded	87	82	104
Real estate - commercial | Owner occupied special purpose
Average Recorded Investment
With no related allowance recorded	574	1,280	2,584
With an allowance recorded			2,150
Interest Income Recognized
With no related allowance recorded			45
Real estate - commercial | Non-owner occupied general purpose
Average Recorded Investment
With no related allowance recorded	1,396	2,939	5,130
With an allowance recorded	123	38	508
Interest Income Recognized
With no related allowance recorded	2	3
Real estate - commercial | Non-owner occupied special purpose
Average Recorded Investment
With no related allowance recorded	506	712	1,042
Real estate - commercial | Retail properties
Average Recorded Investment
With no related allowance recorded	590		1,572
Real estate - commercial | Farm
Average Recorded Investment
With no related allowance recorded	636	636
Real estate - residential | Investor
Average Recorded Investment
With no related allowance recorded	1,873	2,251	4,290
With an allowance recorded		67	410
Interest Income Recognized
With no related allowance recorded	47	51	43
Real estate - residential | Owner occupied
Average Recorded Investment
With no related allowance recorded	10,182	10,979	10,299
With an allowance recorded	457	68	794
Interest Income Recognized
With no related allowance recorded	158	160	187
With an allowance recorded			1
Real estate - residential | Revolving and junior liens
Average Recorded Investment
With no related allowance recorded	2,608	2,484	2,004
With an allowance recorded	23	208	934
Interest Income Recognized
With no related allowance recorded	29	7	6
With an allowance recorded		3
Consumer
Average Recorded Investment
With no related allowance recorded	100
Construction Loans | Real estate - commercial | Homebuilder
Average Recorded Investment
With no related allowance recorded		895	1,903
With an allowance recorded			84
Interest Income Recognized
With no related allowance recorded			82
Construction Loans | Real estate - commercial | Land
Average Recorded Investment
With no related allowance recorded			105
Construction Loans | Real estate - commercial | Commercial speculative
Average Recorded Investment
With no related allowance recorded	78	42	369
With an allowance recorded			587
Construction Loans | Real estate - commercial | All other
Average Recorded Investment
With no related allowance recorded	$ 104	145	147
With an allowance recorded		$ 135	$ 353