Unconsolidated Entities - Summary of Investments in and Advances to our Unconsolidated Entities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule Of Equity Method Investments [Line Items]
Investments in and advances to unconsolidated entities	$ 5,496,450	$ 4,230,429
Unconsolidated Co-Investment Ventures [Member]
Schedule Of Equity Method Investments [Line Items]
Investments in and advances to unconsolidated entities	5,274,702	4,057,524
Other Ventures [Member]
Schedule Of Equity Method Investments [Line Items]
Investments in and advances to unconsolidated entities	$ 221,748	$ 172,905