Investment Components, Including Associated Derivatives (Detail) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Jun. 30, 2015
Cash, Cash Equivalents and Investments [Line Items]
Cost Basis	$ 130,108		$ 119,078
Unrealized Gains	3,752		4,895
Unrealized Losses	(461)		(302)
Recorded Basis	133,399		123,671
Cash and cash equivalents	6,713	$ 8,468	6,510	$ 7,170	$ 7,185	$ 5,595
Short-term Investments	119,305		106,730
Equity and Other Investments	7,381		10,431
Cash
Cash, Cash Equivalents and Investments [Line Items]
Cash	3,390		3,501
Unrealized Gains	0		0
Unrealized Losses	0		0
Cash and cash equivalents	3,390		3,501
Short-term Investments	0		0
Equity and Other Investments	0		0
Mutual funds
Cash, Cash Equivalents and Investments [Line Items]
Cost Basis	1,139		1,012
Unrealized Gains	0		0
Unrealized Losses	0		0
Recorded Basis	1,139		1,012
Cash and cash equivalents	1,139		1,012
Short-term Investments	0		0
Equity and Other Investments	0		0
Commercial paper
Cash, Cash Equivalents and Investments [Line Items]
Cost Basis	536		298
Unrealized Gains	0		0
Unrealized Losses	0		0
Recorded Basis	536		298
Cash and cash equivalents	337		298
Short-term Investments	199		0
Equity and Other Investments	0		0
Certificates of deposit
Cash, Cash Equivalents and Investments [Line Items]
Cost Basis	1,767		1,000
Unrealized Gains	0		0
Unrealized Losses	0		0
Recorded Basis	1,767		1,000
Cash and cash equivalents	1,341		868
Short-term Investments	426		132
Equity and Other Investments	0		0
U.S. government and agency securities
Cash, Cash Equivalents and Investments [Line Items]
Cost Basis	104,688		89,970
Unrealized Gains	75		245
Unrealized Losses	(345)		(11)
Recorded Basis	104,418		90,204
Cash and cash equivalents	102		100
Short-term Investments	104,316		90,104
Equity and Other Investments	0		0
Foreign government bonds
Cash, Cash Equivalents and Investments [Line Items]
Cost Basis	5,344		5,502
Unrealized Gains	2		10
Unrealized Losses	(16)		(18)
Recorded Basis	5,330		5,494
Cash and cash equivalents	404		731
Short-term Investments	4,926		4,763
Equity and Other Investments	0		0
Mortgage- and asset-backed securities
Cash, Cash Equivalents and Investments [Line Items]
Cost Basis	4,241		4,789
Unrealized Gains	16		21
Unrealized Losses	(4)		(2)
Recorded Basis	4,253		4,808
Cash and cash equivalents	0		0
Short-term Investments	4,253		4,808
Equity and Other Investments	0		0
Corporate notes and bonds
Cash, Cash Equivalents and Investments [Line Items]
Cost Basis	4,823		6,509
Unrealized Gains	60		110
Unrealized Losses	(17)		(35)
Recorded Basis	4,866		6,584
Cash and cash equivalents	0		0
Short-term Investments	4,866		6,584
Equity and Other Investments	0		0
Municipal securities
Cash, Cash Equivalents and Investments [Line Items]
Cost Basis	284		285
Unrealized Gains	38		57
Unrealized Losses	0		0
Recorded Basis	322		342
Cash and cash equivalents	0		0
Short-term Investments	322		342
Equity and Other Investments	0		0
Common and preferred stock
Cash, Cash Equivalents and Investments [Line Items]
Cost Basis	3,380		5,597
Unrealized Gains	3,561		4,452
Unrealized Losses	(79)		(236)
Recorded Basis	6,862		9,813
Cash and cash equivalents	0		0
Short-term Investments	0		0
Equity and Other Investments	6,862		9,813
Other investments
Cash, Cash Equivalents and Investments [Line Items]
Cost Basis	516		615
Unrealized Gains	0		0
Unrealized Losses	0		0
Recorded Basis	516		615
Cash and cash equivalents	0		0
Short-term Investments	(3)		(3)
Equity and Other Investments	$ 519		$ 618