Accumulated Other Comprehensive Loss (Components of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net of tax	$ 30,497	$ 117,154	$ 193,610
Pension Benefits [Member] | Accumulated Defined Benefit Plans Adjustment Including Portion Attributable to Noncontrolling Interest [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net of tax	(11,763)	(10,780)
Accumulated other comprehensive loss, tax	$ 6,282	$ 6,282