v3.5.0.2
Unrealized Losses on Investments (Detail) - USD ($)
$ in Millions
Sep. 30, 2016
Jun. 30, 2016
Unrealized Losses on Investments [Line Items]    
Less than 12 Months - Fair Value $ 47,178 $ 12,188
Less than 12 Months - Unrealized Losses (96) (165)
12 Months or Greater - Fair Value 1,601 1,967
12 Months or Greater - Unrealized Losses (136) (137)
Total Fair Value 48,779 14,155
Total Unrealized Losses (232) (302)
U.S. government and agency securities    
Unrealized Losses on Investments [Line Items]    
Less than 12 Months - Fair Value 40,654 5,816
Less than 12 Months - Unrealized Losses (26) (3)
12 Months or Greater - Fair Value 379 432
12 Months or Greater - Unrealized Losses (8) (8)
Total Fair Value 41,033 6,248
Total Unrealized Losses (34) (11)
Foreign government bonds    
Unrealized Losses on Investments [Line Items]    
Less than 12 Months - Fair Value 5,081 3,452
Less than 12 Months - Unrealized Losses (1) (3)
12 Months or Greater - Fair Value 38 35
12 Months or Greater - Unrealized Losses (17) (15)
Total Fair Value 5,119 3,487
Total Unrealized Losses (18) (18)
Mortgage- and asset-backed securities    
Unrealized Losses on Investments [Line Items]    
Less than 12 Months - Fair Value 0 844
Less than 12 Months - Unrealized Losses 0 (1)
12 Months or Greater - Fair Value 214 322
12 Months or Greater - Unrealized Losses (1) (1)
Total Fair Value 214 1,166
Total Unrealized Losses (1) (2)
Corporate notes and bonds    
Unrealized Losses on Investments [Line Items]    
Less than 12 Months - Fair Value 920 1,180
Less than 12 Months - Unrealized Losses (4) (11)
12 Months or Greater - Fair Value 484 788
12 Months or Greater - Unrealized Losses (14) (24)
Total Fair Value 1,404 1,968
Total Unrealized Losses (18) (35)
Common and preferred stock    
Unrealized Losses on Investments [Line Items]    
Less than 12 Months - Fair Value 523 896
Less than 12 Months - Unrealized Losses (65) (147)
12 Months or Greater - Fair Value 486 390
12 Months or Greater - Unrealized Losses (96) (89)
Total Fair Value 1,009 1,286
Total Unrealized Losses $ (161) $ (236)