Employee Benefit Plans (Benefit Obligations in Excess of the Fair Value of Plan Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employee Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	$ 106,218	$ 103,681	$ 105,942
Accumulated benefit obligation	106,218	103,681
Fair value of plan's assets	71,541	66,057	$ 72,296
Projected benefit obligation greater than fair value of plan's assets	34,677	37,624
Accumulated benefit obligation greater than fair value of plan's assets	34,677	37,624
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	102,806	100,336
Accumulated benefit obligation	102,806	100,336
Fair value of plan's assets	71,541	66,057
Projected benefit obligation greater than fair value of plan's assets	31,265	34,279
Accumulated benefit obligation greater than fair value of plan's assets	31,265	34,279
Benefit Equalization Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	3,412	3,345
Accumulated benefit obligation	3,412	3,345
Projected benefit obligation greater than fair value of plan's assets	3,412	3,345
Accumulated benefit obligation greater than fair value of plan's assets	$ 3,412	$ 3,345