Retirement Plans - Change in Benefit Obligations and Plan Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Pension plan
Change in benefit obligation - Pension
Benefit obligation at beginning of year	$ 8,970	$ 11,051
Service cost	223	265	$ 248
Interest cost	406	466	392
Actuarial gain/assumption changes	378	(1,239)
Benefits paid	(50)	(33)
Settlements paid	(22)	(1,540)
Benefit obligation at end of year	9,905	8,970	11,051
Accumulated benefit obligation at end of year	8,475	7,661
Change in Plan Assets
Fair value of plan assets at beginning of year	6,707	7,972
Actual return on plan assets	339	(142)
Employer contribution	0	450
Benefits/expenses paid	(50)	(33)
Settlements paid	(22)	(1,540)
Fair value of plan assets at end of year	6,974	6,707	7,972
Funded status - liability	(2,931)	(2,263)
Amounts recorded in stockholders’ equity
Net actuarial (gain) loss	3,465	3,123
Prior service cost	(61)	(90)
Total amount recorded	3,404	3,033
Amount recorded, net taxes	2,042	1,820
SERP
Change in benefit obligation - Pension
Benefit obligation at beginning of year	7,999	7,431
Service cost	0	0	26
Interest cost	323	278	258
Actuarial gain/assumption changes	129	726
Benefits paid	(436)	(436)
Benefit obligation at end of year	8,015	7,999	$ 7,431
Accumulated benefit obligation at end of year	7,482	7,117
Change in Plan Assets
Funded status - liability	(8,015)	(7,999)
Amounts recorded in stockholders’ equity
Net actuarial (gain) loss	2,248	2,462
Prior service cost	0	0
Total amount recorded	2,248	2,462
Amount recorded, net taxes	$ 1,349	$ 1,477