Commitments, Contingencies and Guarantees - Commitments (Details) $ in Millions	Feb. 29, 2020 USD ($)
Commitments and Guarantees Obligations [Line Items]
2020	$ 6,395.2
2021	522.0
2022 and 2023	10.0
2024 and 2025	19.9
2026 and Later	7.8
Maximum Payout	6,954.9
Equity commitments
Commitments and Guarantees Obligations [Line Items]
2020	9.4
2021	99.0
2022 and 2023	0.0
2024 and 2025	0.0
2026 and Later	7.8
Maximum Payout	116.2
Loan commitments
Commitments and Guarantees Obligations [Line Items]
2020	0.0
2021	295.0
2022 and 2023	10.0
2024 and 2025	15.0
2026 and Later	0.0
Maximum Payout	320.0
Underwriting commitments
Commitments and Guarantees Obligations [Line Items]
2020	292.0
2021	0.0
2022 and 2023	0.0
2024 and 2025	0.0
2026 and Later	0.0
Maximum Payout	292.0
Forward starting reverse repos
Commitments and Guarantees Obligations [Line Items]
2020	4,131.5
2021	0.0
2022 and 2023	0.0
2024 and 2025	0.0
2026 and Later	0.0
Maximum Payout	4,131.5
Forward starting repos
Commitments and Guarantees Obligations [Line Items]
2020	1,962.3
2021	0.0
2022 and 2023	0.0
2024 and 2025	0.0
2026 and Later	0.0
Maximum Payout	1,962.3
Other unfunded commitments
Commitments and Guarantees Obligations [Line Items]
2020	0.0
2021	128.0
2022 and 2023	0.0
2024 and 2025	4.9
2026 and Later	0.0
Maximum Payout	132.9
Forward starting securities purchased under agreements to resell settled within three business days
Commitments and Guarantees Obligations [Line Items]
Maximum Payout	4,124.2
Forward starting securities sold under agreements to repurchase settled within three business days
Commitments and Guarantees Obligations [Line Items]
Maximum Payout	$ 1,953.1