Pension and Other Post-Retirement Benefit Plans (Cash Flows) (Details) - Pension Plans [Member] $ in Thousands	3 Months Ended
Mar. 31, 2019 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 579
Estimated future employer contributions	$ 7,500

Amount of contribution received by defined benefit plan from employer which increases plan assets.

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Name:	us-gaap_DefinedBenefitPlanContributionsByEmployer
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration