Components Of Net Periodic Pension Benefit Cost (Details) - United Kingdom Subsidiary - UK Plan - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 8,085	$ 8,622	$ 10,320
Expected return on plan assets	(13,797)	(13,508)	(14,227)
Amortization of unrecognized loss	2,630	2,942	2,047
Net periodic pension cost (income)	$ (3,082)	$ (1,944)	$ (1,860)