Pensions and Other Postretirement Plans (Fair Value of Pension Plan Assets) (Details 9) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	$ 2,312,706	$ 2,120,127	$ 2,343,471
Fair Value, Recurring [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	2,312,706	2,120,127
Cash equivalents and other short-term investments [Member] | Fair Value, Recurring [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	237,132	271,612
U.S. equities [Member] | Fair Value, Recurring [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	1,439,098	1,115,323
International equities [Member] | Fair Value, Recurring [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	161,377	131,912
U.S. stock index fund [Member] | Fair Value, Recurring [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	322,229	601,395
Private investment fund [Member] | Fair Value, Recurring [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	151,854
Total investments [Member] | Fair Value, Recurring [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	2,311,690	2,120,242
Receivables (Payables) for settlement of investments purchased, net [Member] | Fair Value, Recurring [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	1,016	(115)
Level 1 [Member] | Cash equivalents and other short-term investments [Member] | Fair Value, Recurring [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	2,133	2,068
Level 1 [Member] | U.S. equities [Member] | Fair Value, Recurring [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	1,439,098	1,115,323
Level 1 [Member] | International equities [Member] | Fair Value, Recurring [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	161,377	131,912
Level 1 [Member] | U.S. stock index fund [Member] | Fair Value, Recurring [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 1 [Member] | Private investment fund [Member] | Fair Value, Recurring [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0
Level 1 [Member] | Total investments [Member] | Fair Value, Recurring [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	1,602,608	1,249,303
Level 2 [Member] | Cash equivalents and other short-term investments [Member] | Fair Value, Recurring [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	234,999	269,544
Level 2 [Member] | U.S. equities [Member] | Fair Value, Recurring [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 2 [Member] | International equities [Member] | Fair Value, Recurring [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 2 [Member] | U.S. stock index fund [Member] | Fair Value, Recurring [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 2 [Member] | Private investment fund [Member] | Fair Value, Recurring [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0
Level 2 [Member] | Total investments [Member] | Fair Value, Recurring [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	234,999	269,544
Level 3 [Member] | Cash equivalents and other short-term investments [Member] | Fair Value, Recurring [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 3 [Member] | U.S. equities [Member] | Fair Value, Recurring [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 3 [Member] | International equities [Member] | Fair Value, Recurring [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 3 [Member] | U.S. stock index fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	322,229	601,395	706,202
Level 3 [Member] | U.S. stock index fund [Member] | Fair Value, Recurring [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	322,229	601,395
Level 3 [Member] | Private investment fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	151,854	0	$ 0
Level 3 [Member] | Private investment fund [Member] | Fair Value, Recurring [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	151,854
Level 3 [Member] | Total investments [Member] | Fair Value, Recurring [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	$ 474,083	$ 601,395