Fair Value Measurements - Recurring Fair Value Measurements (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Aug. 31, 2023	Aug. 31, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities Segregated under Other Regulations	$ 225,715	$ 238,124
Other assets	89,592	58,280
Total assets	636,544	840,648
Total liabilities	368,275	402,788
Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities Segregated under Other Regulations	0
Other assets	0	0
Total assets	0	0
Total liabilities	0	0
Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities Segregated under Other Regulations	0
Other assets	0	0
Total assets	315,893	543,083
Total liabilities	360,774	392,532
Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities Segregated under Other Regulations	225,715	238,124
Other assets	89,592	58,280
Total assets	320,651	297,565
Total liabilities	7,501	10,256
Commodity derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Instruments and Hedges, Liabilities	354,476	390,139
Derivative Instruments and Hedges, Assets	288,835	491,321
Commodity derivatives | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Instruments and Hedges, Liabilities	0	0
Derivative Instruments and Hedges, Assets	0	0
Commodity derivatives | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Instruments and Hedges, Liabilities	346,975	379,883
Derivative Instruments and Hedges, Assets	283,491	490,160
Commodity derivatives | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Instruments and Hedges, Liabilities	7,501	10,256
Derivative Instruments and Hedges, Assets	5,344	1,161
Foreign currency derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign Currency Contract, Asset, Fair Value Disclosure	32,402	52,923
Foreign Currency Contracts, Liability, Fair Value Disclosure	13,799	12,649
Foreign currency derivatives | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign Currency Contract, Asset, Fair Value Disclosure	0	0
Foreign Currency Contracts, Liability, Fair Value Disclosure	0	0
Foreign currency derivatives | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign Currency Contract, Asset, Fair Value Disclosure	32,402	52,923
Foreign Currency Contracts, Liability, Fair Value Disclosure	13,799	12,649
Foreign currency derivatives | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign Currency Contract, Asset, Fair Value Disclosure	0	0
Foreign Currency Contracts, Liability, Fair Value Disclosure	$ 0	$ 0