Commitments, Contingencies and Guarantees - Additional Information (Detail) £ in Millions, $ in Millions |
1 Months Ended | 6 Months Ended |
|---|---|---|
|
Mar. 31, 2016
GBP (£)
|
May 31, 2016
USD ($)
|
|
| Loss Contingencies [Line Items] | ||
| Contractual obligation | £ | £ 8.1 | |
| Contractual obligation period for 18 years | 18 years | |
| Loan commitments outstanding to clients | $ 226.6 | |
| Fair value of mortgage-related commitments | 165.4 | |
| Fair value of derivative contracts approximated deemed to meet the definition of a guarantee | 363.5 | |
| Maximum amount payable under guarantee | 21.6 | |
| Standby Letters of Credit [Member] | ||
| Loss Contingencies [Line Items] | ||
| Letters of credit commitments | $ 34.3 | |
| Standby letters of credit expiration period | 2 years | |
| Jefferies Capital Partners LLC [Member] | ||
| Loss Contingencies [Line Items] | ||
| Outstanding equity commitments | $ 23.3 | |
| Other Investments [Member] | ||
| Loss Contingencies [Line Items] | ||
| Outstanding equity commitments | $ 4.3 |