Investment Components, Including Associated Derivatives but Excluding Held to Maturity Investments (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014
Cash, Cash Equivalents and Investments [Line Items]
Cost Basis	$ 109,854		$ 103,647
Unrealized Gains	4,994		5,220
Unrealized Losses	(719)		(313)
Recorded Basis	114,129		108,554
Cash and cash equivalents	7,185	$ 5,431	5,595	$ 6,426	$ 6,302	$ 8,669
Short-term Investments	95,455		90,931
Equity and Other Investments	11,489		12,028
Cash
Cash, Cash Equivalents and Investments [Line Items]
Cash	3,480		3,679
Unrealized Gains	0		0
Unrealized Losses	0		0
Cash	3,480		3,679
Cash and cash equivalents	3,480		3,679
Short-term Investments	0		0
Equity and Other Investments	0		0
Mutual funds
Cash, Cash Equivalents and Investments [Line Items]
Cost Basis	1,428		1,100
Unrealized Gains	0		0
Unrealized Losses	0		0
Recorded Basis	1,428		1,100
Cash and cash equivalents	1,428		1,100
Short-term Investments	0		0
Equity and Other Investments	0		0
Commercial paper
Cash, Cash Equivalents and Investments [Line Items]
Cost Basis	790		1
Unrealized Gains	0		0
Unrealized Losses	0		0
Recorded Basis	790		1
Cash and cash equivalents	790		1
Short-term Investments	0		0
Equity and Other Investments	0		0
Certificates of deposit
Cash, Cash Equivalents and Investments [Line Items]
Cost Basis	1,062		906
Unrealized Gains	0		0
Unrealized Losses	0		0
Recorded Basis	1,062		906
Cash and cash equivalents	921		776
Short-term Investments	141		130
Equity and Other Investments	0		0
U.S. government and agency securities
Cash, Cash Equivalents and Investments [Line Items]
Cost Basis	79,113		72,843
Unrealized Gains	11		76
Unrealized Losses	(232)		(30)
Recorded Basis	78,892		72,889
Cash and cash equivalents	350		39
Short-term Investments	78,542		72,850
Equity and Other Investments	0		0
Foreign government bonds
Cash, Cash Equivalents and Investments [Line Items]
Cost Basis	4,973		5,477
Unrealized Gains	3		3
Unrealized Losses	(39)		(24)
Recorded Basis	4,937		5,456
Cash and cash equivalents	216		0
Short-term Investments	4,721		5,456
Equity and Other Investments	0		0
Mortgage- and asset-backed securities
Cash, Cash Equivalents and Investments [Line Items]
Cost Basis	4,849		4,899
Unrealized Gains	17		23
Unrealized Losses	(9)		(6)
Recorded Basis	4,857		4,916
Cash and cash equivalents	0		0
Short-term Investments	4,857		4,916
Equity and Other Investments	0		0
Corporate notes and bonds
Cash, Cash Equivalents and Investments [Line Items]
Cost Basis	6,914		7,192
Unrealized Gains	65		97
Unrealized Losses	(106)		(37)
Recorded Basis	6,873		7,252
Cash and cash equivalents	0		0
Short-term Investments	6,873		7,252
Equity and Other Investments	0		0
Municipal securities
Cash, Cash Equivalents and Investments [Line Items]
Cost Basis	285		285
Unrealized Gains	36		35
Unrealized Losses	0		(1)
Recorded Basis	321		319
Cash and cash equivalents	0		0
Short-term Investments	321		319
Equity and Other Investments	0		0
Common and preferred stock
Cash, Cash Equivalents and Investments [Line Items]
Cost Basis	6,395		6,668
Unrealized Gains	4,862		4,986
Unrealized Losses	(333)		(215)
Recorded Basis	10,924		11,439
Cash and cash equivalents	0		0
Short-term Investments	0		0
Equity and Other Investments	10,924		11,439
Other investments
Cash, Cash Equivalents and Investments [Line Items]
Cost Basis	565		597
Unrealized Gains	0		0
Unrealized Losses	0		0
Recorded Basis	565		597
Cash and cash equivalents	0		0
Short-term Investments	0		8
Equity and Other Investments	$ 565		$ 589