Derivative Financial Instruments Foreign Currency Exchange Rate Risk (Details) $ in Thousands, £ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019 USD ($) $ / £	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) $ / £	Sep. 30, 2018 USD ($)	Sep. 30, 2019 GBP (£) $ / £	Mar. 25, 2015 USD ($)	Mar. 25, 2015 GBP (£)
Derivative [Line Items]
Foreign subsidiaries third-party debt denominated in local currencies	$ 948,400		$ 948,400
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	$ 100	$ 200	800	$ 500
Derivative Instruments, Gain (Loss) Reclassification from Accumulated OCI to Income, Estimated Net Amount to be Transferred			$ 200
Settlement Date			Mar. 31, 2020
Intercompany Loan [Member]
Derivative [Line Items]
Long-term Debt, Gross						$ 181,000	£ 120.0
Minimum [Member] | Foreign Exchange Forward, Settled [Member]
Derivative [Line Items]
Exchange Rate | $ / £	1.50		1.50		1.50
Minimum [Member] | British Pound Foreign currency forward contracts [Member]
Derivative [Line Items]
Exchange Rate | $ / £	1.28		1.28		1.28
Maximum [Member] | Foreign Exchange Forward, Settled [Member]
Derivative [Line Items]
Exchange Rate | $ / £	1.51		1.51		1.51
Maximum [Member] | British Pound Foreign currency forward contracts [Member]
Derivative [Line Items]
Exchange Rate | $ / £	1.57		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