Fair Value Measurements - Fair Value Measurements (Details) - Fair Value, Recurring [Member] - USD ($) $ in Thousands	May 31, 2024	Aug. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities Segregated under Other Regulations	$ 150,648	$ 225,715
Other assets	155,808	89,592
Total assets	518,748	636,544
Foreign exchange derivatives		13,799
Total liabilities	203,008	368,275
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities Segregated under Other Regulations	150,648	225,715
Other assets	155,808	89,592
Total assets	307,523	320,651
Foreign exchange derivatives		0
Total liabilities	3,311	7,501
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities Segregated under Other Regulations	0	0
Other assets	0	0
Total assets	211,225	315,893
Foreign exchange derivatives		13,799
Total liabilities	199,697	360,774
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities Segregated under Other Regulations	0	0
Other assets	0	0
Total assets	0	0
Foreign exchange derivatives		0
Total liabilities	0	0
Commodity derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	198,434	288,835
Derivative Liability	180,416	354,476
Commodity derivatives | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	1,067	5,344
Derivative Liability	3,311	7,501
Commodity derivatives | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	197,367	283,491
Derivative Liability	177,105	346,975
Commodity derivatives | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	0	0
Derivative Liability	0	0
Foreign exchange derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign exchange derivatives	13,858	32,402
Foreign exchange derivatives	22,592
Foreign exchange derivatives | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign exchange derivatives	0	0
Foreign exchange derivatives	0
Foreign exchange derivatives | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign exchange derivatives	13,858	32,402
Foreign exchange derivatives	22,592
Foreign exchange derivatives | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign exchange derivatives	0	$ 0
Foreign exchange derivatives	$ 0