Commitments, Contingencies and Guarantees - External Credit Ratings of Underlying or Referenced Assets for Credit Related Derivatives Contracts (Detail) $ in Millions	Nov. 30, 2015 USD ($)
Index credit default swaps [Member]
Credit Derivatives [Line Items]
External credit ratings	$ 698.4
Single name credit default swaps [Member]
Credit Derivatives [Line Items]
External credit ratings	382.4
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	264.3
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	50.6
AAA/Aaa [Member] | Index credit default swaps [Member]
Credit Derivatives [Line Items]
External credit ratings	698.4
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	10.0
BBB/Baa [Member] | Index credit default swaps [Member]
Credit Derivatives [Line Items]
External credit ratings	0.0
BBB/Baa [Member] | Single name credit default swaps [Member]
Credit Derivatives [Line Items]
External credit ratings	$ 57.5