Acquisitions, Goodwill and Intangible Assets - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2012 USD ($) Segment	Jan. 05, 2012 USD ($)	Jan. 05, 2012 EUR (€)	Dec. 31, 2011 USD ($)	Dec. 31, 2012 Private Equity USD ($)	Dec. 31, 2012 Real Estate USD ($)	Dec. 31, 2012 Hedge Fund Solutions USD ($)	Dec. 31, 2012 Credit USD ($)	Dec. 31, 2012 Financial Advisory USD ($)
Business Acquisition [Line Items]
Purchase price in cash		$ 232,000,000	€ 181,400,000
Acquisition-related costs	2,100,000
Number of business segments	5
Goodwill, carrying value	1,703,602,000			1,703,602,000	694,500,000	421,700,000	172,100,000	346,400,000	68,900,000
Expected amortization of intangibles, 2013	88,300,000
Expected amortization of intangibles, 2014	83,400,000
Expected amortization of intangibles, 2015	77,100,000
Expected amortization of intangibles, 2016	72,800,000
Expected amortization of intangibles, 2017	$ 46,400,000
Intangible assets expected to amortize over a weighted-average period	8 years 7 months 6 days