Unconsolidated Entities - Earnings on Investment in Co-Investment Ventures (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Schedule of Equity Method Investments [Line Items]
Earnings from unconsolidated entities, net	$ 8,421	$ 3,889	$ 33,189	$ 17,884
Private capital revenue	43,608	30,993	77,243	63,350
Unconsolidated co-investment ventures [Member]
Schedule of Equity Method Investments [Line Items]
Earnings from unconsolidated entities, net	7,871	1,153	32,166	12,911
Total Investment management revenue	42,911	30,494	76,343	61,908
Private capital revenue	43,244	30,496	77,723	61,986
Unconsolidated co-investment ventures [Member] | Development management and other income - Europe [Member]
Schedule of Equity Method Investments [Line Items]
Total Investment management revenue	333	2	1,380	78
Unconsolidated co-investment ventures [Member] | Americas [Member]
Schedule of Equity Method Investments [Line Items]
Earnings from unconsolidated entities, net	(874)	(6,749)	13,394	(4,466)
Total Investment management revenue	14,818	16,081	30,895	33,604
Unconsolidated co-investment ventures [Member] | Europe [Member]
Schedule of Equity Method Investments [Line Items]
Earnings from unconsolidated entities, net	8,761	7,172	16,303	15,169
Total Investment management revenue	13,854	9,325	24,467	18,462
Unconsolidated co-investment ventures [Member] | Asia [Member]
Schedule of Equity Method Investments [Line Items]
Earnings from unconsolidated entities, net	(16)	730	2,469	2,208
Total Investment management revenue	$ 14,239	$ 5,088	$ 20,981	$ 9,842