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Summary of Significant Accounting Policies - Non-cash Investing and Financing Activities (Detail) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Other Significant Noncash Transactions [Line Items]      
Accounts payable related to construction in progress $ 13,400 $ 13,300 $ 31,600
Dividends declared 78,549 75,245 68,600
Casualty insurance receivable and reduction of real estate assets, net related to hurricane casualty 65,900 0 0
Redemption of OP Units 0 0 18,300
Mortgages assumed from acquisitions 0 0 33,700
Elimination of a previously held equity interest 0 0 1,400
Building [Member]      
Other Significant Noncash Transactions [Line Items]      
Assumption of buildings due to lease termination $ 8,600 $ 0 $ 0