Related Party Transactions - Due to Affiliates (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	May 21, 2012	Dec. 31, 2011
Related Party Transaction [Line Items]
Due to non-consolidated affiliates		$ 18.3
Total	332.1		108.5
Affiliated Entity [Member]
Related Party Transaction [Line Items]
Due to affiliates of Consolidated Funds	42.1		37.3
Due to non-consolidated affiliates	27.8		44.4
Contingent consideration related to acquisitions	216.2
Amounts owed under the tax receivable agreement	34.9
Other	$ 11.1		$ 26.8