Unrealized Losses on Debt Investments (Detail) - USD ($) $ in Millions	Mar. 31, 2023	Jun. 30, 2022
Unrealized Losses on Investments [Line Items]
Less than 12 Months - Fair Value	$ 15,258	$ 69,641
Less than 12 Months - Unrealized Losses	(407)	(2,368)
12 Months or Greater - Fair Value	49,960	3,138
12 Months or Greater - Unrealized Losses	(3,397)	(446)
Total Fair Value	65,218	72,779
Total Unrealized Losses	(3,804)	(2,814)
U.S. government and agency securities
Unrealized Losses on Investments [Line Items]
Less than 12 Months - Fair Value	12,922	59,092
Less than 12 Months - Unrealized Losses	(354)	(1,835)
12 Months or Greater - Fair Value	41,520	2,210
12 Months or Greater - Unrealized Losses	(2,817)	(352)
Total Fair Value	54,442	61,302
Total Unrealized Losses	(3,171)	(2,187)
Foreign government bonds
Unrealized Losses on Investments [Line Items]
Less than 12 Months - Fair Value	74	418
Less than 12 Months - Unrealized Losses	(5)	(18)
12 Months or Greater - Fair Value	390	27
12 Months or Greater - Unrealized Losses	(18)	(6)
Total Fair Value	464	445
Total Unrealized Losses	(23)	(24)
Mortgage- and asset-backed securities
Unrealized Losses on Investments [Line Items]
Less than 12 Months - Fair Value	160	510
Less than 12 Months - Unrealized Losses	(5)	(26)
12 Months or Greater - Fair Value	387	41
12 Months or Greater - Unrealized Losses	(31)	(4)
Total Fair Value	547	551
Total Unrealized Losses	(36)	(30)
Corporate notes and bonds
Unrealized Losses on Investments [Line Items]
Less than 12 Months - Fair Value	2,015	9,443
Less than 12 Months - Unrealized Losses	(41)	(477)
12 Months or Greater - Fair Value	7,486	786
12 Months or Greater - Unrealized Losses	(511)	(77)
Total Fair Value	9,501	10,229
Total Unrealized Losses	(552)	(554)
Municipal securities
Unrealized Losses on Investments [Line Items]
Less than 12 Months - Fair Value	87	178
Less than 12 Months - Unrealized Losses	(2)	(12)
12 Months or Greater - Fair Value	177	74
12 Months or Greater - Unrealized Losses	(20)	(7)
Total Fair Value	264	252
Total Unrealized Losses	$ (22)	$ (19)