Employee Benefit Plans (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined benefit plan, discretionary contribution by employer	$ 5,500,000	$ 0
Minimum required contribution for 2017	0
Contributions to the CERP	439,000	21,000	$ 20,000
Accumulated benefit obligation	120,700,000	116,700,000
Defined Benefit Plan, Amount to be Amortized from Accumulated Other Comprehensive Income (Loss) Next Fiscal Year	2,100,000
Interest cost on projected benefit obligation	$ 3,826,000	$ 3,944,000	$ 4,762,000
Expected long-term rate of return on pension plan assets	6.00%	6.00%	6.00%
Annualized 10-year return for pension plan	6.30%
Rate of return	9.60%	7.20%
Pension expense	$ 704,000
Expected pension expense for the upcoming fiscal year	$ 761,000
Equity securities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Long-term investment target mix	35.00%
Fixed Income Securities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Long-term investment target mix	65.00%
Change due to updated mortality projection scale [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Change in pension plan obligations due to change in mortality assumptions	$ (300,000)
Change in Accounting Estimate, Type [Domain]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Interest cost on projected benefit obligation		$ (900,000)