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Retirement Plans (Components Of Net Periodic Pension Benefit Cost) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Net periodic pension cost (income)	$ 100,000	$ 100,000
UK Plan | United Kingdom Subsidiary [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	1,336,000	1,596,000
Expected return on plan assets	(3,192,000)	(2,997,000)
Amortization of unrecognized loss	913,000	595,000
Net periodic pension cost (income)	$ (943,000)	$ (806,000)

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