Auto Loans Held for Investment (Past Due Receivables) (Details) - USD ($) $ in Millions	May 31, 2025	Feb. 28, 2025
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss, Current	$ 16,214.8	$ 16,740.7
Past due receivables as a percentage of total auto loans held for investment	5.48%	4.85%
Financing Receivable, before Allowance for Credit Loss, Noncurrent	$ 939.7	$ 853.9
Financing Receivable, before Allowance for Credit Loss	$ 17,154.5	$ 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	94.52%	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	3.24%	2.98%
Financing Receivable, before Allowance for Credit Loss, Noncurrent	$ 555.8	$ 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	1.80%	1.49%
Financing Receivable, before Allowance for Credit Loss, Noncurrent	$ 308.9	$ 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	0.44%	0.38%
Financing Receivable, before Allowance for Credit Loss, Noncurrent	$ 75.0	$ 67.1
Tier 1
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss, Current	15,773.6	16,199.5
Financing Receivable, before Allowance for Credit Loss, Noncurrent	805.9	730.8
Financing Receivable, before Allowance for Credit Loss	16,579.5	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	484.5	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	257.5	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	63.9	57.1
Tier 1 | Credit Grade A
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss, Current	9,655.3	9,543.3
Financing Receivable, before Allowance for Credit Loss, Noncurrent	62.3	57.4
Financing Receivable, before Allowance for Credit Loss	9,717.6	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	41.0	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	15.6	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	5.7	5.9
Tier 1 | Credit Grade B
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss, Current	5,091.4	5,491.5
Financing Receivable, before Allowance for Credit Loss, Noncurrent	484.1	437.6
Financing Receivable, before Allowance for Credit Loss	5,575.5	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	297.4	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	148.1	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	38.6	34.3
Tier 1 | Credit Grade C And Other
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss, Current	1,026.9	1,164.7
Financing Receivable, before Allowance for Credit Loss, Noncurrent	259.5	235.8
Financing Receivable, before Allowance for Credit Loss	1,286.4	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	146.1	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	93.8	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	19.6	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	441.2	541.2
Financing Receivable, before Allowance for Credit Loss, Noncurrent	133.8	123.1
Financing Receivable, before Allowance for Credit Loss	575.0	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	71.3	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	51.4	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	$ 11.1	$ 10.0