Pension and Other Postretirement Benefits (Schedule of Total Expense for All Retirement Plans) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) plan	Dec. 31, 2018 USD ($) plan	Dec. 31, 2017 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Total retirement plan expense	$ 2,960	$ 2,927	$ 3,044
Multiemployer plans withdrawal obligation	4,200
401(k) plan
Defined Benefit Plan Disclosure [Line Items]
Total retirement plan expense	2,419	2,262	2,248
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Total retirement plan expense	346	427	476
Multiemployer and other defined benefit and pension plans
Defined Benefit Plan Disclosure [Line Items]
Total retirement plan expense	$ 195	$ 238	$ 320
Number of plans | plan	1	3
Multiemployer Plans Exited | Multiemployer and other defined benefit and pension plans
Defined Benefit Plan Disclosure [Line Items]
Number of plans | plan	2