Unconsolidated Entities - Summary of Amounts Recognized in Consolidated Statements of Income Related to Co-Investment Ventures (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule Of Equity Method Investments [Line Items]
Total strategic capital revenues		$ 373,889	$ 303,562	$ 217,829
Total earnings from unconsolidated co-investment ventures, net		248,567	206,307	159,262
Unconsolidated Co-Investment Ventures [Member]
Schedule Of Equity Method Investments [Line Items]
Total strategic capital revenues	[1]	371,257	301,175	215,075
Total earnings from unconsolidated co-investment ventures, net		234,168	191,877	155,402
Unconsolidated Co-Investment Ventures [Member] | U.S. [Member]
Schedule Of Equity Method Investments [Line Items]
Total strategic capital revenues		174,586	37,911	36,964
Total earnings from unconsolidated co-investment ventures, net		32,989	10,441	7,124
Unconsolidated Co-Investment Ventures [Member] | Other Americas [Member]
Schedule Of Equity Method Investments [Line Items]
Total strategic capital revenues		28,493	22,799	22,735
Total earnings from unconsolidated co-investment ventures, net		26,200	27,155	28,842
Unconsolidated Co-Investment Ventures [Member] | Europe [Member]
Schedule Of Equity Method Investments [Line Items]
Total strategic capital revenues		106,768	186,113	112,626
Total earnings from unconsolidated co-investment ventures, net		145,792	137,652	106,656
Unconsolidated Co-Investment Ventures [Member] | Asia [Member]
Schedule Of Equity Method Investments [Line Items]
Total strategic capital revenues		61,410	54,352	42,750
Total earnings from unconsolidated co-investment ventures, net		$ 29,187	$ 16,629	$ 12,780

[1] We earned promote revenue (third-party share) of $127.5 million, $88.5 million and $29.5 million in 2017, 2016 and 2015, respectively. Promote revenue is based on the venture’s cumulative returns to investors over a certain time-period, generally three years.