Unconsolidated Entities - Investments in Co-Investment Ventures by Region (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Schedule Of Equity Method Investments Joint Ventures [Line Items]
Investments in and advances to unconsolidated entities	$ 4,210,305	$ 2,195,782
Unconsolidated Co-Investment Ventures [Member]
Schedule Of Equity Method Investments Joint Ventures [Line Items]
Equity method investment, percentage	30.40%	25.10%
Investments in and advances to unconsolidated entities	4,035,790	2,013,080
Americas [Member] | Unconsolidated Co-Investment Ventures [Member]
Schedule Of Equity Method Investments Joint Ventures [Line Items]
Equity method investment, percentage	23.50%	23.20%
Investments in and advances to unconsolidated entities	1,211,275	1,111,831
Europe [Member] | Unconsolidated Co-Investment Ventures [Member]
Schedule Of Equity Method Investments Joint Ventures [Line Items]
Equity method investment, percentage	41.30%	29.70%
Investments in and advances to unconsolidated entities	2,492,282	722,748
Asia [Member] | Unconsolidated Co-Investment Ventures [Member]
Schedule Of Equity Method Investments Joint Ventures [Line Items]
Equity method investment, percentage	15.10%	19.20%
Investments in and advances to unconsolidated entities	$ 332,233	$ 178,501