Unconsolidated Entities - Investments in Co-Investment Ventures by Region (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Schedule Of Equity Method Investments Joint Ventures [Line Items]
Investments in and advances to unconsolidated entities	$ 3,635,214	$ 2,195,782
Unconsolidated Co-Investment Ventures [Member]
Schedule Of Equity Method Investments Joint Ventures [Line Items]
Weighted average ownership percentage in co-investment ventures	27.00%	25.10%
Investments in and advances to unconsolidated entities	3,458,229	2,013,080
Unconsolidated Co-Investment Ventures [Member] | Americas [Member]
Schedule Of Equity Method Investments Joint Ventures [Line Items]
Weighted average ownership percentage in co-investment ventures	21.30%	23.20%
Investments in and advances to unconsolidated entities	1,124,636	1,111,831
Unconsolidated Co-Investment Ventures [Member] | Europe [Member]
Schedule Of Equity Method Investments Joint Ventures [Line Items]
Weighted average ownership percentage in co-investment ventures	36.80%	29.70%
Investments in and advances to unconsolidated entities	2,041,583	722,748
Unconsolidated Co-Investment Ventures [Member] | Asia [Member]
Schedule Of Equity Method Investments Joint Ventures [Line Items]
Weighted average ownership percentage in co-investment ventures	17.00%	19.20%
Investments in and advances to unconsolidated entities	$ 292,010	$ 178,501