Risk Management and Use of Derivative Financial Instruments - Narratives (Details)	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2016 EUR (€)	Dec. 31, 2015 EUR (€)
Derivatives, Fair Value [Line Items]
Cash collateral	$ 0	$ 0
Footnote Details
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	$ 8,581,000	29,317,000	$ 23,395,000
Summary of Derivative Instruments
Derivative, Remaining Maturity	77 months
Total credit exposure on derivatives	$ 54,500,000
Derivatives, net liability position	3,300,000	8,200,000
Aggregate termination value for immediate settlement	3,300,000	8,300,000
Senior Unsecured Credit Facility - Revolver	676,715,000	485,021,000
Senior Unsecured Notes, net	1,807,200,000	1,476,084,000
Senior Unsecured Notes
Summary of Derivative Instruments
Senior Unsecured Notes, net	1,827,100,000	1,494,400,000
Senior Unsecured Notes | 2.0% Senior Notes
Summary of Derivative Instruments
Senior Unsecured Credit Facility - Revolver | €				€ 272,000,000	€ 361,000,000
Senior Unsecured Notes, net	$ 527,100,000	544,400,000
Principal Amount | €				€ 500,000,000
Debt instrument stated interest rate	2.00%			2.00%
Individual Counterparty
Summary of Derivative Instruments
Total credit exposure on derivatives	$ 29,500,000
Interest expense
Summary of Derivative Instruments
Estimated amount reclassified from OCI to income, derivatives	800,000
Other Income
Summary of Derivative Instruments
Estimated amount reclassified from OCI to income, derivatives	14,400,000
Cash Flow Hedging
Footnote Details
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	7,304,000	5,338,000	(2,794,000)
Equity method investments | Cash Flow Hedging
Footnote Details
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	200,000	600,000	300,000
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	$ 0	$ 0	$ 400,000