Pensions and Other Postretirement Benefit Plans (Schedule of Fair Value of Plan Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other postretirement benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	178,942	205,586	$ 180,672
Pension Plans [Member] | Total investments in the fair value hierarchy [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	84,713	87,358
Pension Plans [Member] | Quoted Prices in Active Markets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,300	3,588
Pension Plans [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	78,523	81,363
Common Stocks and Equity Funds [Member] | Other postretirement benefits [Member] | Quoted Prices in Active Markets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	284	335
Common Stocks and Equity Funds [Member] | Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	284	335
Investment of plan assets	42,852	37,768
Common Stocks and Equity Funds [Member] | Pension Plans [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets
Common Stocks and Equity Funds [Member] | Pension Plans [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets
Debt Securities [Member] | Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	78,523	81,363
Debt Securities [Member] | Pension Plans [Member] | Quoted Prices in Active Markets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets
Debt Securities [Member] | Pension Plans [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	78,523	81,363
Debt Securities [Member] | Pension Plans [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets
Fixed income funds [Member] | Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Investment of plan assets	47,534	75,881
Insurance Contracts [Member] | Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,890	2,407
Insurance Contracts [Member] | Pension Plans [Member] | Quoted Prices in Active Markets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets
Insurance Contracts [Member] | Pension Plans [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets
Cash and Short-Term Investments [Member] | Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,016	3,253
Cash and Short-Term Investments [Member] | Pension Plans [Member] | Quoted Prices in Active Markets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,016	3,253
Cash and Short-Term Investments [Member] | Pension Plans [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets
Cash and Short-Term Investments [Member] | Pension Plans [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets
Limited Partnerships [Member] | Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Investment of plan assets	$ 3,843	$ 4,579