Summary of Significant Accounting Policies (Narrative) (Details)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) segment	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Period in which short-term investment become cash equivalents			90 days
Interest capitalized	$ 3,800,000	$ 2,400,000	$ 11,400,000	$ 9,900,000
Compensation costs, leasing and construction activities	18,700,000	17,200,000	52,700,000	43,000,000
Cash flows from capitalized leasing costs			31,400,000	37,800,000
Goodwill	780,099,000		$ 780,099,000		$ 330,664,000
Award vesting period			4 years
Unrecognized tax benefits	0		$ 0		0
Income tax penalties and interest expense	0	0	$ 0	0
Number of reportable segments | segment			1
Total operating revenues	546,293,000	435,989,000	$ 1,565,426,000	1,262,893,000
Rental property operating and maintenance	177,192,000	140,538,000	490,909,000	394,640,000
Global revolving credit facility
Summary Of Significant Accounting Policies [Line Items]
Deferred financing costs	11,600,000		11,600,000		7,600,000
Unsecured term loan
Summary Of Significant Accounting Policies [Line Items]
Deferred financing costs	$ 6,500,000		$ 6,500,000		1,300,000
Accounting Standards Update 2015-03 | Deferred Financing Costs, Net
Summary Of Significant Accounting Policies [Line Items]
Deferred financing costs					(35,200,000)
Accounting Standards Update 2015-03 | Long-Term Line of Credit | Global revolving credit facility
Summary Of Significant Accounting Policies [Line Items]
Deferred financing costs					7,600,000
Accounting Standards Update 2015-03 | Long-Term Line of Credit | Unsecured term loan
Summary Of Significant Accounting Policies [Line Items]
Deferred financing costs					1,300,000
Accounting Standards Update 2015-03 | Unsecured Debt
Summary Of Significant Accounting Policies [Line Items]
Deferred financing costs					26,000,000
Accounting Standards Update 2015-03 | Secured Debt
Summary Of Significant Accounting Policies [Line Items]
Deferred financing costs					$ 300,000
Restatement Adjustment
Summary Of Significant Accounting Policies [Line Items]
Rental property operating and maintenance		$ (1,700,000)		$ (4,500,000)
Sales
Summary Of Significant Accounting Policies [Line Items]
Concentration risk	12.10%	12.70%	10.80%	12.70%
Long-Lived Assets
Summary Of Significant Accounting Policies [Line Items]
Concentration risk			17.60%		18.80%
United States
Summary Of Significant Accounting Policies [Line Items]
Total operating revenues	$ 423,800,000	$ 334,500,000	$ 1,200,000,000	$ 1,000,000,000
Long-lived assets	6,200,000,000		6,200,000,000		$ 6,000,000,000
Outside The United States
Summary Of Significant Accounting Policies [Line Items]
Total operating revenues	122,500,000	101,400,000	321,800,000	291,300,000
Long-lived assets	2,800,000,000		2,800,000,000		2,600,000,000
United Kingdom
Summary Of Significant Accounting Policies [Line Items]
Total operating revenues	66,100,000	$ 55,200,000	169,400,000	$ 160,100,000
Long-lived assets	$ 1,600,000,000		$ 1,600,000,000		$ 1,600,000,000