Derivative Financial Instruments Foreign Currency Exchange Rate Risk (Details) $ in Thousands, £ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 GBP (£) $ / £	Jun. 30, 2019 USD ($) $ / £	Mar. 25, 2015 GBP (£)	Mar. 25, 2015 USD ($)
Derivative [Line Items]
Foreign subsidiaries third-party debt denominated in local currencies						$ 1,000,000
Proceeds from settlement of derivative transactions			$ 45,360	$ 0
Foreign Exchange Forward, Settled [Member]
Derivative [Line Items]
Notional Amount | £					£ 120.0
British Pound Foreign currency forward contracts [Member]
Derivative [Line Items]
Notional Amount | £					£ 32.6
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion	$ 500	$ 200	700	$ 300
Existing net gains expected to be realized within the next 12 months			$ 300
Settlement Date			Mar. 31, 2020
Intercompany Loan [Member]
Derivative [Line Items]
Long-term Debt, Gross							£ 120.0	$ 181,000
Minimum [Member] | Foreign Exchange Forward, Settled [Member]
Derivative [Line Items]
Exchange Rate | $ / £					1.50	1.50
Minimum [Member] | British Pound Foreign currency forward contracts [Member]
Derivative [Line Items]
Exchange Rate | $ / £					1.28	1.28
Maximum [Member] | Foreign Exchange Forward, Settled [Member]
Derivative [Line Items]
Exchange Rate | $ / £					1.51	1.51
Maximum [Member] | British Pound Foreign currency forward contracts [Member]
Derivative [Line Items]
Exchange Rate | $ / £					1.57	1.57
Designated as Hedging Instrument [Member] | British Pound Foreign currency forward contracts [Member]
Derivative [Line Items]
Proceeds from settlement of derivative transactions			$ 26,088