Auto Loans Held for Investment (Allowance for Loan Losses) (Details) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Aug. 31, 2025	Aug. 31, 2024	Aug. 31, 2025	Aug. 31, 2024	Feb. 28, 2025	May 31, 2025	May 31, 2024	Feb. 29, 2024
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	$ 507,286,000	$ 500,800,000	$ 507,286,000	$ 500,800,000	$ 458,730,000	$ 474,200,000	$ 493,100,000	$ 482,800,000
Financing Receivable, Allowance for Credit Loss, Writeoff	(168,700,000)	(163,800,000)	(310,400,000)	(296,900,000)	$ (589,200,000)
Financing Receivable, Allowance for Credit Loss, Recovery	59,600,000	58,900,000	115,100,000	121,100,000
Provision for Loan, Lease, and Other Losses	142,200,000	112,600,000	243,904,000	193,798,000
Item As Percent Of Total Ending Managed Receivables, Period Increase (Decrease)			41
Revenue from Contract with Customer, Excluding Assessed Tax	6,594,700,000	$ 7,013,500,000	14,141,200,000	$ 14,126,900,000
Transfer of auto loans held for sale
Financing Receivable, Allowance for Credit Loss [Line Items]
Provision for Loan, Lease, and Other Losses	(15,700,000)		(42,200,000)
Auto loans held for investment
Financing Receivable, Allowance for Credit Loss [Line Items]
Provision for Loan, Lease, and Other Losses	$ 157,900,000		$ 286,100,000
Allowance For Loan Losses, percent
Financing Receivable, Allowance for Credit Loss [Line Items]
Item as percent of total ending managed receivables	3.02%	2.82%	3.02%	2.82%	2.61%	2.76%	2.79%	2.78%
Tier 1
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	$ 423,200,000	$ 417,300,000	$ 423,200,000	$ 417,300,000	$ 378,100,000	$ 395,800,000	$ 396,600,000	$ 389,700,000
Financing Receivable, Allowance for Credit Loss, Writeoff	(141,300,000)	(131,100,000)	(261,500,000)	(244,100,000)
Financing Receivable, Allowance for Credit Loss, Recovery	51,400,000	52,100,000	100,200,000	106,000,000.0
Provision for Loan, Lease, and Other Losses		99,700,000		165,700,000
Tier 1 | Transfer of auto loans held for sale
Financing Receivable, Allowance for Credit Loss [Line Items]
Provision for Loan, Lease, and Other Losses	(11,200,000)		(30,300,000)
Tier 1 | Auto loans held for investment
Financing Receivable, Allowance for Credit Loss [Line Items]
Provision for Loan, Lease, and Other Losses	128,500,000		236,700,000
Tier 2 & Tier 3
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	84,100,000	83,500,000	84,100,000	83,500,000	$ 80,600,000	$ 78,400,000	$ 96,500,000	$ 93,100,000
Financing Receivable, Allowance for Credit Loss, Writeoff	(27,400,000)	(32,700,000)	(48,900,000)	(52,800,000)
Financing Receivable, Allowance for Credit Loss, Recovery	8,200,000	6,800,000	14,900,000	15,100,000
Provision for Loan, Lease, and Other Losses		$ 12,900,000		$ 28,100,000
Tier 2 & Tier 3 | Transfer of auto loans held for sale
Financing Receivable, Allowance for Credit Loss [Line Items]
Provision for Loan, Lease, and Other Losses	(4,500,000)		(11,900,000)
Tier 2 & Tier 3 | Auto loans held for investment
Financing Receivable, Allowance for Credit Loss [Line Items]
Provision for Loan, Lease, and Other Losses	$ 29,400,000		$ 49,400,000