Unrealized Losses on Debt Investments (Detail) - USD ($) $ in Millions	Mar. 31, 2024	Jun. 30, 2023
Unrealized Losses on Investments [Line Items]
Less than 12 Months - Fair Value	$ 1,998	$ 10,721
Less than 12 Months - Unrealized Losses	(31)	(398)
12 Months or Greater - Fair Value	55,281	53,598
12 Months or Greater - Unrealized Losses	(3,460)	(4,152)
Total Fair Value	57,279	64,319
Total Unrealized Losses	(3,491)	(4,550)
U.S. government and agency securities
Unrealized Losses on Investments [Line Items]
Less than 12 Months - Fair Value	650	7,950
Less than 12 Months - Unrealized Losses	(17)	(336)
12 Months or Greater - Fair Value	48,044	45,273
12 Months or Greater - Unrealized Losses	(3,057)	(3,534)
Total Fair Value	48,694	53,223
Total Unrealized Losses	(3,074)	(3,870)
Foreign government bonds
Unrealized Losses on Investments [Line Items]
Less than 12 Months - Fair Value	40	77
Less than 12 Months - Unrealized Losses	0	(5)
12 Months or Greater - Fair Value	226	391
12 Months or Greater - Unrealized Losses	(12)	(19)
Total Fair Value	266	468
Total Unrealized Losses	(12)	(24)
Mortgage- and asset-backed securities
Unrealized Losses on Investments [Line Items]
Less than 12 Months - Fair Value	264	257
Less than 12 Months - Unrealized Losses	(4)	(5)
12 Months or Greater - Fair Value	339	412
12 Months or Greater - Unrealized Losses	(30)	(34)
Total Fair Value	603	669
Total Unrealized Losses	(34)	(39)
Corporate notes and bonds
Unrealized Losses on Investments [Line Items]
Less than 12 Months - Fair Value	1,000	2,326
Less than 12 Months - Unrealized Losses	(9)	(49)
12 Months or Greater - Fair Value	6,435	7,336
12 Months or Greater - Unrealized Losses	(332)	(534)
Total Fair Value	7,435	9,662
Total Unrealized Losses	(341)	(583)
Municipal securities
Unrealized Losses on Investments [Line Items]
Less than 12 Months - Fair Value	44	111
Less than 12 Months - Unrealized Losses	(1)	(3)
12 Months or Greater - Fair Value	237	186
12 Months or Greater - Unrealized Losses	(29)	(31)
Total Fair Value	281	297
Total Unrealized Losses	$ (30)	$ (34)