Commitments, Contingencies and Guarantees - Commitments and Contingencies (Detail) $ in Millions	3 Months Ended
	Feb. 28, 2018 USD ($)
Other Commitments [Line Items]
2018	$ 6,308.7
2019	295.2
2020 and 2021	77.5
2022 and 2023	114.4
2024 and Later	102.0
Maximum Payout	$ 6,897.8
Guarantor obligation settled period (in days)	3 days
Equity commitments
Other Commitments [Line Items]
2018	$ 0.0
2019	0.2
2020 and 2021	18.7
2022 and 2023	0.0
2024 and Later	96.5
Maximum Payout	115.4
Loan commitments
Other Commitments [Line Items]
2018	140.7
2019	0.0
2020 and 2021	47.5
2022 and 2023	7.4
2024 and Later	0.0
Maximum Payout	195.6
Mortgage-related and other purchase commitments
Other Commitments [Line Items]
2018	0.0
2019	177.7
2020 and 2021	0.0
2022 and 2023	0.0
2024 and Later	0.0
Maximum Payout	177.7
Underwriting commitments
Other Commitments [Line Items]
2018	55.0
2019	0.0
2020 and 2021	0.0
2022 and 2023	0.0
2024 and Later	0.0
Maximum Payout	55.0
Forward starting reverse repos
Other Commitments [Line Items]
2018	3,432.2
2019	0.0
2020 and 2021	0.0
2022 and 2023	0.0
2024 and Later	0.0
Maximum Payout	3,432.2
Forward starting repos
Other Commitments [Line Items]
2018	2,523.5
2019	0.0
2020 and 2021	0.0
2022 and 2023	0.0
2024 and Later	0.0
Maximum Payout	2,523.5
Other unfunded commitments
Other Commitments [Line Items]
2018	157.3
2019	117.3
2020 and 2021	11.3
2022 and 2023	107.0
2024 and Later	5.5
Maximum Payout	$ 398.4