Commitments, Contingencies and Guarantees - Commitments (Detail) $ in Millions	May 31, 2019 USD ($)
Commitments and Guarantees Obligations [Line Items]
2019	$ 7,428.8
2020	374.5
2021 and 2022	198.1
2023 and 2024	5.6
2025 and Later	17.8
Maximum Payout	8,024.8
Equity commitments
Commitments and Guarantees Obligations [Line Items]
2019	0.0
2020	124.5
2021 and 2022	0.3
2023 and 2024	0.0
2025 and Later	13.0
Maximum Payout	137.8
Loan commitments
Commitments and Guarantees Obligations [Line Items]
2019	0.0
2020	250.0
2021 and 2022	55.0
2023 and 2024	5.6
2025 and Later	0.0
Maximum Payout	310.6
Underwriting commitments
Commitments and Guarantees Obligations [Line Items]
2019	264.2
2020	0.0
2021 and 2022	0.0
2023 and 2024	0.0
2025 and Later	0.0
Maximum Payout	264.2
Forward starting reverse repos
Commitments and Guarantees Obligations [Line Items]
2019	4,410.9
2020	0.0
2021 and 2022	0.0
2023 and 2024	0.0
2025 and Later	0.0
Maximum Payout	4,410.9
Forward starting repos
Commitments and Guarantees Obligations [Line Items]
2019	2,635.7
2020	0.0
2021 and 2022	0.0
2023 and 2024	0.0
2025 and Later	0.0
Maximum Payout	2,635.7
Other unfunded commitments
Commitments and Guarantees Obligations [Line Items]
2019	118.0
2020	0.0
2021 and 2022	142.8
2023 and 2024	0.0
2025 and Later	4.8
Maximum Payout	265.6
Forward starting securities purchased under agreements to resell settled within three business days
Commitments and Guarantees Obligations [Line Items]
Maximum Payout	4,401.6
Forward starting securities purchased under agreements to repurchase settled within three business days
Commitments and Guarantees Obligations [Line Items]
Maximum Payout	$ 2,136.0