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Retirement Plans (Narrative) (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($) plan	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) plan	Sep. 30, 2019 USD ($)
UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Number of plans | plan	3		3
Contributions to defined benefit pension plans			$ 100,000
Net periodic pension cost (income)	$ 100,000	$ 100,000	200,000	$ 200,000
UK Plan | United Kingdom Subsidiary [Member]
Defined Benefit Plan Disclosure [Line Items]
Contributions to defined benefit pension plans			3,400,000
Anticipated additional contribution	1,300,000		1,300,000
Net periodic pension cost (income)	$ (815,000)	$ (450,000)	$ (2,406,000)	$ (1,397,000)

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