Auto Loans Held for Investment (Past Due Receivables) (Details) - USD ($) $ in Millions	Aug. 31, 2025	Feb. 28, 2025
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss, Current	$ 15,835.6	$ 16,740.7
Past due receivables as a percentage of total auto loans held for investment	5.63%	4.85%
Financing Receivable, before Allowance for Credit Loss, Noncurrent	$ 944.1	$ 853.9
Financing Receivable, before Allowance for Credit Loss	$ 16,779.7	$ 17,594.6
Item As A Percent Of Total Auto Loans Held for Investment	100.00%	100.00%
One to Thirty Days Past Due
Financing Receivable, Past Due [Line Items]
Past due receivables as a percentage of total auto loans held for investment	94.37%	95.15%
Thirty One To Sixty Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Past due receivables as a percentage of total auto loans held for investment	3.16%	2.98%
Financing Receivable, before Allowance for Credit Loss, Noncurrent	$ 530.2	$ 523.9
Sixty One To Ninety Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Past due receivables as a percentage of total auto loans held for investment	2.02%	1.49%
Financing Receivable, before Allowance for Credit Loss, Noncurrent	$ 338.6	$ 262.9
Greater Than Ninety Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Past due receivables as a percentage of total auto loans held for investment	0.45%	0.38%
Financing Receivable, before Allowance for Credit Loss, Noncurrent	$ 75.3	$ 67.1
Tier 1
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss, Current	15,420.2	16,199.5
Financing Receivable, before Allowance for Credit Loss, Noncurrent	809.0	730.8
Financing Receivable, before Allowance for Credit Loss	16,229.2	16,930.3
Tier 1 | Thirty One To Sixty Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss, Noncurrent	460.9	452.0
Tier 1 | Sixty One To Ninety Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss, Noncurrent	284.0	221.7
Tier 1 | Greater Than Ninety Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss, Noncurrent	64.1	57.1
Tier 1 | Credit Grade A
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss, Current	9,633.3	9,543.3
Financing Receivable, before Allowance for Credit Loss, Noncurrent	58.8	57.4
Financing Receivable, before Allowance for Credit Loss	9,692.1	9,600.7
Tier 1 | Credit Grade A | Thirty One To Sixty Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss, Noncurrent	36.7	36.7
Tier 1 | Credit Grade A | Sixty One To Ninety Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss, Noncurrent	16.7	14.8
Tier 1 | Credit Grade A | Greater Than Ninety Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss, Noncurrent	5.4	5.9
Tier 1 | Credit Grade B
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss, Current	4,789.4	5,491.5
Financing Receivable, before Allowance for Credit Loss, Noncurrent	490.5	437.6
Financing Receivable, before Allowance for Credit Loss	5,279.9	5,929.1
Tier 1 | Credit Grade B | Thirty One To Sixty Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss, Noncurrent	286.9	276.0
Tier 1 | Credit Grade B | Sixty One To Ninety Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss, Noncurrent	164.3	127.3
Tier 1 | Credit Grade B | Greater Than Ninety Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss, Noncurrent	39.3	34.3
Tier 1 | Credit Grade C And Other
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss, Current	997.5	1,164.7
Financing Receivable, before Allowance for Credit Loss, Noncurrent	259.7	235.8
Financing Receivable, before Allowance for Credit Loss	1,257.2	1,400.5
Tier 1 | Credit Grade C And Other | Thirty One To Sixty Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss, Noncurrent	137.3	139.3
Tier 1 | Credit Grade C And Other | Sixty One To Ninety Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss, Noncurrent	103.0	79.6
Tier 1 | Credit Grade C And Other | Greater Than Ninety Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss, Noncurrent	19.4	16.9
Tier 2 & Tier 3 | Credit Grade C And Other
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss, Current	415.4	541.2
Financing Receivable, before Allowance for Credit Loss, Noncurrent	135.1	123.1
Financing Receivable, before Allowance for Credit Loss	550.5	664.3
Tier 2 & Tier 3 | Credit Grade C And Other | Thirty One To Sixty Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss, Noncurrent	69.3	71.9
Tier 2 & Tier 3 | Credit Grade C And Other | Sixty One To Ninety Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss, Noncurrent	54.6	41.2
Tier 2 & Tier 3 | Credit Grade C And Other | Greater Than Ninety Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss, Noncurrent	$ 11.2	$ 10.0