Commitments, Contingencies and Guarantees (Commitments and Contingencies) (Details) $ in Millions	Feb. 28, 2019 USD ($)
Commitments And Guarantee Obligations [Line Items]
2019	$ 11,612.3
2020	153.6
2021 and 2022	146.2
2023 and 2024	34.9
2025 and Later	509.8
Maximum Payout	$ 12,456.8
Guarantor obligation settled period	3 days
Equity commitments
Commitments And Guarantee Obligations [Line Items]
2019	$ 17.2
2020	148.6
2021 and 2022	1.3
2023 and 2024	0.0
2025 and Later	9.8
Maximum Payout	176.9
Loan commitments
Commitments And Guarantee Obligations [Line Items]
2019	250.0
2020	5.0
2021 and 2022	54.0
2023 and 2024	30.0
2025 and Later	500.0
Maximum Payout	839.0
Underwriting commitments
Commitments And Guarantee Obligations [Line Items]
2019	215.4
2020	0.0
2021 and 2022	0.0
2023 and 2024	0.0
2025 and Later	0.0
Maximum Payout	215.4
Forward starting reverse repos
Commitments And Guarantee Obligations [Line Items]
2019	6,225.6
2020	0.0
2021 and 2022	0.0
2023 and 2024	0.0
2025 and Later	0.0
Maximum Payout	6,225.6
Forward starting repos
Commitments And Guarantee Obligations [Line Items]
2019	4,738.8
2020	0.0
2021 and 2022	0.0
2023 and 2024	0.0
2025 and Later	0.0
Maximum Payout	4,738.8
Other unfunded commitments
Commitments And Guarantee Obligations [Line Items]
2019	165.3
2020	0.0
2021 and 2022	90.9
2023 and 2024	4.9
2025 and Later	0.0
Maximum Payout	261.1
Forward starting securities purchased under agreements to resell settled
Commitments And Guarantee Obligations [Line Items]
Maximum Payout	6,225.4
Forward starting securities purchased under agreements to repurchase settled
Commitments And Guarantee Obligations [Line Items]
Maximum Payout	$ 4,736.0