v3.26.1
POSTRETIREMENT BENEFITS AND EMPLOYEE STOCK OWNERSHIP PLAN - Additional Information (Details) - USD ($)
$ / shares in Units, shares in Thousands
 12 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 1991
Jun. 30, 1989
Defined Benefit Plan Disclosure [Line Items]          
Defined contribution expense $ 534,000,000 $ 534,000,000 $ 425,000,000    
Accumulated benefit obligation $ 11,800,000,000 $ 12,500,000,000      
Series A Preferred Stock          
Defined Benefit Plan Disclosure [Line Items]          
Allocated (in shares) 18,000 21,000 23,000    
Series B Preferred Stock          
Defined Benefit Plan Disclosure [Line Items]          
Allocated (in shares) 36,365 34,965 33,723    
Pension Benefits          
Defined Benefit Plan Disclosure [Line Items]          
Expected return on plan assets (in percent) 6.00% 6.00% 6.00%    
Expected future employer contributions, next fiscal year $ 200,000,000        
Pension Benefits | Series A Preferred Stock          
Defined Benefit Plan Disclosure [Line Items]          
ESOP, direct loan amount         $ 1,000,000,000.0
ESOP, debt structure, employer loan guarantee $ 0        
Dividend (in dollars per share) $ 4.26        
Liquidation value (in dollars per share) $ 6.82        
Other Retiree Benefits          
Defined Benefit Plan Disclosure [Line Items]          
Expected return on plan assets (in percent) 8.50% 8.50% 8.50%    
Expected future employer contributions, next fiscal year $ 59,000,000        
Other Retiree Benefits | Series B Preferred Stock          
Defined Benefit Plan Disclosure [Line Items]          
ESOP, direct loan amount       $ 1,000,000,000.0  
ESOP, debt structure, employer loan guarantee $ 596,000,000        
Dividend (in dollars per share) $ 4.26        
Liquidation value (in dollars per share) $ 12.96        
Treasury Stock          
Defined Benefit Plan Disclosure [Line Items]          
Expected return on plan assets (in percent) 8.50%        
Minimum | Equity securities          
Defined Benefit Plan Disclosure [Line Items]          
Expected return on plan assets (in percent) 8.00%        
Minimum | Debt securities          
Defined Benefit Plan Disclosure [Line Items]          
Expected return on plan assets (in percent) 3.00%        
Maximum | Equity securities          
Defined Benefit Plan Disclosure [Line Items]          
Expected return on plan assets (in percent) 9.00%        
Maximum | Debt securities          
Defined Benefit Plan Disclosure [Line Items]          
Expected return on plan assets (in percent) 5.00%        
United States          
Defined Benefit Plan Disclosure [Line Items]          
Contribution rate (in percent) 12.00% 12.00% 13.00%