Commitments, Contingencies and Guarantees - External Credit Ratings of Underlying or Referenced Assets for Credit Related Derivatives Contracts (Detail) $ in Millions	Feb. 29, 2016 USD ($)
Index credit default swaps [Member]
Credit Derivatives [Line Items]
External credit ratings	$ 52.5
Single name credit default swaps [Member]
Credit Derivatives [Line Items]
External credit ratings	237.2
Below Investment Grade [Member] | Index credit default swaps [Member]
Credit Derivatives [Line Items]
External credit ratings	0.0
Below Investment Grade [Member] | Single name credit default swaps [Member]
Credit Derivatives [Line Items]
External credit ratings	164.6
Unrated [Member] | Index credit default swaps [Member]
Credit Derivatives [Line Items]
External credit ratings	0.0
Unrated [Member] | Single name credit default swaps [Member]
Credit Derivatives [Line Items]
External credit ratings	51.1
AAA/Aaa [Member] | Index credit default swaps [Member]
Credit Derivatives [Line Items]
External credit ratings	3.5
AAA/Aaa [Member] | Single name credit default swaps [Member]
Credit Derivatives [Line Items]
External credit ratings	0.0
AA/Aa [Member] | Index credit default swaps [Member]
Credit Derivatives [Line Items]
External credit ratings	0.0
AA/Aa [Member] | Single name credit default swaps [Member]
Credit Derivatives [Line Items]
External credit ratings	0.0
A [Member] | Index credit default swaps [Member]
Credit Derivatives [Line Items]
External credit ratings	0.0
A [Member] | Single name credit default swaps [Member]
Credit Derivatives [Line Items]
External credit ratings	0.0
BBB/Baa [Member] | Index credit default swaps [Member]
Credit Derivatives [Line Items]
External credit ratings	49.0
BBB/Baa [Member] | Single name credit default swaps [Member]
Credit Derivatives [Line Items]
External credit ratings	$ 21.5