Commitments and Contingencies - Unfunded Commitments (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013
Operating Statistics [Line Items]
Total unfunded commitments	$ 2,296.3
Corporate Private Equity [Member]
Operating Statistics [Line Items]
Total unfunded commitments	1,887.9
Global Market Strategies [Member]
Operating Statistics [Line Items]
Total unfunded commitments	221.1
Real Assets [Member]
Operating Statistics [Line Items]
Total unfunded commitments	$ 187.3