Nature of Business and Financial Statement Presentation - Non-cash Investing and Financing Activities (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Noncash Or Part Noncash Acquisitions [Line Items]
Mortgages assumed from acquisitions			$ 293,300,000	$ 148,500,000
Issuance of Operating Partnership Units ("OP Units") in connection with acquisitions			18,256,000	0
Preferred equity interest and mezzanine loan applied to purchase price			51,775,000	0
Elimination of the previously held equity interest in unconsolidated joint ventures acquired			2,800,000	15,400,000
Reclassification adjustment of foreign currency translation	5,609,000	0	25,324,000	0
Accounts payable related to construction in progress			31,300,000	25,100,000
Dividends declared	61,323,000	49,800,000	61,323,000	49,800,000
Write-off of preferred share original issuance costs	0	0	1,943,000	5,246,000
Accumulated Other Comprehensive Loss
Noncash Or Part Noncash Acquisitions [Line Items]
Reclassification adjustment of foreign currency translation			$ 21,360,000	$ 0