Retirement Plan (Changes in Benefit Obligation and Plan Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension plan's benefit obligation - beginning of year	$ 21,201	$ 23,633
Service cost	1,294	1,694	$ 895
Interest cost	787	819	638
Participant contributions	244	593
Amendments	21	0
Benefits paid	(2,171)	(2,260)
Actuarial loss (gain)	(2,384)	(3,278)
Pension plan's benefit obligation - end of year	18,992	21,201	23,633
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets - beginning of year	0	0
Benefits paid	(2,171)	(2,260)
Employer contributions	1,927	1,667
Participant contributions	244	593
Fair value of plan assets - end of year	0	0	$ 0
Defined Benefit Plan, Funded Status of Plan	(18,992)	(21,201)
Accrued post-retirement plan liability	(18,992)	(21,201)
Cumulative actuarial loss	771	(1,613)
Prior service credit	32,434	35,937
Total	$ 33,205	$ 34,324