Loans - Loan sales Narrative (Details) - USD ($) $ in Millions	12 Months Ended
May 31, 2026	May 31, 2025	May 31, 2024
Receivables [Abstract]
Proceeds from sale of loans and leases held-for-investment	$ 671	$ 424	$ 324
Loans held for sale	$ 4	$ 21

Amount, before valuation allowance, of financing receivable classified as held-for-sale.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481990/310-10-45-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 948
-SubTopic 310
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477011/948-310-45-1

Name:	us-gaap_LoansReceivableHeldForSaleAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant