v3.21.2
Unrealized Losses on Debt Investments (Detail) - USD ($)
$ in Millions
Sep. 30, 2021
Jun. 30, 2021
Unrealized Losses on Investments [Line Items]    
Less than 12 Months - Fair Value $ 9,925 $ 11,389
Less than 12 Months - Unrealized Losses (118) (132)
12 Months or Greater - Fair Value 849 127
12 Months or Greater - Unrealized Losses (47) (3)
Total Fair Value 10,774 11,516
Total Unrealized Losses (165) (135)
U.S. government and agency securities    
Unrealized Losses on Investments [Line Items]    
Less than 12 Months - Fair Value 5,420 5,294
Less than 12 Months - Unrealized Losses (98) (111)
12 Months or Greater - Fair Value 604 0
12 Months or Greater - Unrealized Losses (36) 0
Total Fair Value 6,024 5,294
Total Unrealized Losses (134) (111)
Foreign government bonds    
Unrealized Losses on Investments [Line Items]    
Less than 12 Months - Fair Value 1,215 3,148
Less than 12 Months - Unrealized Losses (3) (1)
12 Months or Greater - Fair Value 8 5
12 Months or Greater - Unrealized Losses (1) (1)
Total Fair Value 1,223 3,153
Total Unrealized Losses (4) (2)
Mortgage- and asset-backed securities    
Unrealized Losses on Investments [Line Items]    
Less than 12 Months - Fair Value 1,240 1,211
Less than 12 Months - Unrealized Losses (5) (5)
12 Months or Greater - Fair Value 140 87
12 Months or Greater - Unrealized Losses (2) (1)
Total Fair Value 1,380 1,298
Total Unrealized Losses (7) (6)
Corporate notes and bonds    
Unrealized Losses on Investments [Line Items]    
Less than 12 Months - Fair Value 2,030 1,678
Less than 12 Months - Unrealized Losses (12) (8)
12 Months or Greater - Fair Value 43 34
12 Months or Greater - Unrealized Losses (1) (1)
Total Fair Value 2,073 1,712
Total Unrealized Losses (13) (9)
Municipal securities    
Unrealized Losses on Investments [Line Items]    
Less than 12 Months - Fair Value 20 58
Less than 12 Months - Unrealized Losses 0 (7)
12 Months or Greater - Fair Value 54 1
12 Months or Greater - Unrealized Losses (7) 0
Total Fair Value 74 59
Total Unrealized Losses $ (7) $ (7)