Derivative Financial Instruments - External Credit Ratings of Underlyings or Referenced Assets (Details) - USD ($) $ in Millions	Aug. 31, 2018	Nov. 30, 2017
Index credit default swaps
Derivative [Line Items]
Total Notional	$ 18.0	$ 49.0
Single name credit default swaps
Derivative [Line Items]
Total Notional	70.2	218.2
Investment Grade | Index credit default swaps
Derivative [Line Items]
Total Notional	3.0	3.0
Investment Grade | Single name credit default swaps
Derivative [Line Items]
Total Notional	32.5	129.1
Non-investment Grade | Index credit default swaps
Derivative [Line Items]
Total Notional	15.0	46.0
Non-investment Grade | Single name credit default swaps
Derivative [Line Items]
Total Notional	34.8	$ 89.1
Unrated | Index credit default swaps
Derivative [Line Items]
Total Notional	0.0
Unrated | Single name credit default swaps
Derivative [Line Items]
Total Notional	$ 2.9