Derivative Financial Instruments Cash Flow Impact of Settled Derivative Transactions (Details) $ in Thousands, € in Millions	6 Months Ended
	Jun. 30, 2019 EUR (€)	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)
Derivative [Line Items]
Proceeds from settlement of derivative transactions		$ 45,360	$ 0
Designated as Hedging Instrument [Member] | British Pound Foreign currency forward contracts [Member]
Derivative [Line Items]
Proceeds from settlement of derivative transactions		26,088
Not Designated as Hedging Instrument [Member] | Currency Swap [Member]
Derivative [Line Items]
Proceeds from settlement of derivative transactions	€ 17.0	$ 19,272