Fair Value Measurement - Additional Information (Details)	6 Months Ended
	Nov. 30, 2020 USD ($)	Nov. 30, 2021 USD ($) borrower	May 31, 2021 USD ($) borrower
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets		$ 31,773,375,000	$ 31,118,667,000
Total financial liabilities		$ 30,056,245,000	$ 29,418,975,000
Change in unrealized gain (loss) recorded in earnings	$ 0
Number of borrowers | borrower		892	892
Outstanding amount	27,051,163,000	$ 28,934,814,000	$ 28,415,107,000
Loans, fair value		$ 30,768,917,000	$ 29,967,692,000
Nonperforming financial instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of borrowers | borrower		2	4
Outstanding amount		$ 219,444,000	$ 237,497,000
Nonperforming financial instruments | Collateral-dependent Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Outstanding amount		0
RTFC
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Outstanding amount		431,641,000	$ 420,383,000
RTFC | Nonperforming financial instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of borrowers | borrower			2
Outstanding amount		0	$ 9,185,000
RTFC | Nonperforming financial instruments | Collateral-dependent Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of borrowers | borrower			2
Outstanding amount			$ 9,000,000
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets		30,768,917,000	29,967,692,000
Total financial liabilities		11,069,168,000	10,589,164,000
Loans, fair value		30,768,917,000	29,967,692,000
Level 3 | Recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	0	0
Total financial liabilities	$ 0	$ 0
Level 3 | RTFC | Nonperforming financial instruments | Fair Value, Nonrecurring | Collateral-dependent Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, fair value			$ 6,000,000