Related Party Transactions - Due to Affiliates (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Related Party Transactions [Abstract]
Due to affiliates of Consolidated Funds	$ 0.0	$ 0.2
Due to non-consolidated affiliates	75.7	29.7
Performance-based contingent cash consideration related to acquisitions	37.5	36.1
Amounts owed under the tax receivable agreement	94.0	137.8
Other	22.7	19.8
Total	$ 229.9	$ 223.6