Fair Value of Financial Instruments - Fair Value, Liabilities Measured on Recurring Basis (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
OPP
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity fair value	$ (12,400)	$ (14,300)
Cross currency swaps, net (GBP & EUR)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset fair value	1,606	3,042
Foreign currency forwards, net (GBP & EUR)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset fair value	3,390	2,203
Interest rate swaps, net (GBP & EUR)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liability fair value	(16,093)	(5,461)
Quoted Prices in Active Markets Level 1 | OPP
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity fair value	0	0
Quoted Prices in Active Markets Level 1 | Cross currency swaps, net (GBP & EUR)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset fair value	0	0
Quoted Prices in Active Markets Level 1 | Foreign currency forwards, net (GBP & EUR)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset fair value	0	0
Quoted Prices in Active Markets Level 1 | Interest rate swaps, net (GBP & EUR)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liability fair value	0	0
Significant Other Observable Inputs Level 2 | OPP
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity fair value	0	0
Significant Other Observable Inputs Level 2 | Cross currency swaps, net (GBP & EUR)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset fair value	1,606	3,042
Significant Other Observable Inputs Level 2 | Foreign currency forwards, net (GBP & EUR)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset fair value	3,390	2,203
Significant Other Observable Inputs Level 2 | Interest rate swaps, net (GBP & EUR)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liability fair value	(16,093)	(5,461)
Significant Unobservable Inputs Level 3 | OPP
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity fair value	(12,400)	(14,300)
Significant Unobservable Inputs Level 3 | Cross currency swaps, net (GBP & EUR)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset fair value	0	0
Significant Unobservable Inputs Level 3 | Foreign currency forwards, net (GBP & EUR)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset fair value	0	0
Significant Unobservable Inputs Level 3 | Interest rate swaps, net (GBP & EUR)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liability fair value	$ 0	$ 0