v3.26.1
AVAILABLE-FOR-SALE SECURITIES, Gross Unrealized Losses and Fair Value and Significant Assumptions (Details) - USD ($)
$ in Millions
Mar. 31, 2026
Sep. 30, 2025
Debt Securities, Available-for-sale [Line Items]    
Fair value less than 12 months $ 479 $ 241
Unrealized losses less than 12 months (2) 0
Fair value 12 months or more 5,074 5,737
Unrealized losses 12 months or more (481) (532)
Fair value 5,553 5,978
Unrealized losses (483) (532)
Agency residential MBS    
Debt Securities, Available-for-sale [Line Items]    
Fair value less than 12 months 200 23
Unrealized losses less than 12 months (1) 0
Fair value 12 months or more 2,690 2,994
Unrealized losses 12 months or more (238) (265)
Fair value 2,890 3,017
Unrealized losses (239) (265)
Agency commercial MBS    
Debt Securities, Available-for-sale [Line Items]    
Fair value less than 12 months 5 0
Unrealized losses less than 12 months 0 0
Fair value 12 months or more 976 1,129
Unrealized losses 12 months or more (71) (85)
Fair value 981 1,129
Unrealized losses (71) (85)
Agency CMOs    
Debt Securities, Available-for-sale [Line Items]    
Fair value less than 12 months 156 2
Unrealized losses less than 12 months (1) 0
Fair value 12 months or more 908 978
Unrealized losses 12 months or more (139) (147)
Fair value 1,064 980
Unrealized losses (140) (147)
U.S. Treasuries    
Debt Securities, Available-for-sale [Line Items]    
Fair value less than 12 months 50 215
Unrealized losses less than 12 months 0 0
Fair value 12 months or more 8 9
Unrealized losses 12 months or more 0 0
Fair value 58 224
Unrealized losses 0 0
Other agency obligations    
Debt Securities, Available-for-sale [Line Items]    
Fair value less than 12 months 43 0
Unrealized losses less than 12 months 0 0
Fair value 12 months or more 109 227
Unrealized losses 12 months or more (1) (2)
Fair value 152 227
Unrealized losses (1) (2)
Non-agency residential MBS    
Debt Securities, Available-for-sale [Line Items]    
Fair value less than 12 months 19 0
Unrealized losses less than 12 months 0 0
Fair value 12 months or more 366 380
Unrealized losses 12 months or more (31) (32)
Fair value 385 380
Unrealized losses (31) (32)
Corporate bonds    
Debt Securities, Available-for-sale [Line Items]    
Fair value less than 12 months 5 0
Unrealized losses less than 12 months 0 0
Fair value 12 months or more 13 15
Unrealized losses 12 months or more 0 (1)
Fair value 18 15
Unrealized losses 0 (1)
Other    
Debt Securities, Available-for-sale [Line Items]    
Fair value less than 12 months 1 1
Unrealized losses less than 12 months 0 0
Fair value 12 months or more 4 5
Unrealized losses 12 months or more (1) 0
Fair value 5 6
Unrealized losses $ (1) $ 0