Investment Securities - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Feb. 28, 2026	Feb. 28, 2025	Feb. 28, 2026	Feb. 28, 2025	May 31, 2025
Debt and Equity Securities, FV-NI [Line Items]
Debt securities, unrealized gains	$ 1	$ 1	$ 1	$ 7
Proceeds for sale of debt investment securities	0	0	16	14
Debt securities, realized gains			0	1
Equity securities, unrealized (loss) gain	(1)	$ (1)	(1)	$ 1
Common Stock
Debt and Equity Securities, FV-NI [Line Items]
Equity securities, fair value	$ 10		$ 10		$ 11