Accumulated Other Comprehensive Income (Loss) (Components of Accumulated Other Comprehensive Income (Loss)) (Details) - Accumulated Defined Benefit Plans Adjustment Including Portion Attributable to Noncontrolling Interest [Member] - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net of tax	$ (8,145)	$ (8,188)
Pension Benefits [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net of tax	(10,167)	(10,304)
Accumulated other comprehensive loss, tax	6,282	6,282
Postretirement Benefit Plan [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net of tax	2,022	2,116
Accumulated other comprehensive loss, tax	$ 527	$ 527

Accumulated Other Comprehensive Income (Loss) (Components of Accumulated Other Comprehensive Income (Loss)) (Details) - Accumulated Defined Benefit Plans Adjustment Including Portion Attributable to Noncontrolling Interest [Member] - USD ($)
$ in Thousands

Mar. 31, 2019

Dec. 31, 2018

Accumulated Other Comprehensive Income (Loss) [Line Items]

Accumulated other comprehensive loss, net of tax

$ (8,145)

$ (8,188)

Pension Benefits [Member]

Accumulated Other Comprehensive Income (Loss) [Line Items]

Accumulated other comprehensive loss, net of tax

(10,167)

(10,304)

Accumulated other comprehensive loss, tax