Fair Value of Financial Instruments Financial Instruments Carried at Fair Value-Level 2 (Details) - Fair Value, Inputs, Level 2 [Member] - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets carried at fair value	$ 3,055	$ 45,695
Financial liabilities carried at fair value	63,428	14,454
Interest rate swap agreements [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability	60,220	14,395
British pound forward contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	3,055	26,011
Derivative Liability	14	59
Cross-currency swap contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	0	19,684
Cross-currency swap contract [Member] | Net Investment Hedging [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability	807	0
Cross-currency swap contract [Member] | Fair Value Measurement [Domain]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability	$ 2,387	$ 0