Fair Value of Financial Instruments Financial Instruments Carried at Fair Value-Level 2 (Details) - Fair Value, Inputs, Level 2 [Member] - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets carried at fair value	$ 36,846	$ 45,695
Financial liabilities carried at fair value	32,378	14,454
British pound forward contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	23,198	26,011
Derivative Liability	191	59
Cross-currency swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	13,648	19,684
Interest rate swap agreements [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability	$ 32,187	$ 14,395