ACCUMULATED OTHER COMPREHENSIVE INCOME - STATEMENT OF AOCI (Details) - USD ($) $ in Millions		12 Months Ended
		Jun. 30, 2020		Jun. 30, 2019		Jun. 30, 2018
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax		$ (14,936)		$ (14,749)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax		(1,546)	[1]	(89)	[2]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax		301	[3]	229	[4]
Other Comprehensive Income (Loss), Net of Tax		(1,245)		140		$ (119)
Adoption of New Accounting Standard_Reclass from AOCI to Retained Earnings	[5]			(326)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest		(16)		1
Accumulated Other Comprehensive Income (Loss), Net of Tax		(16,165)		(14,936)		(14,749)
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Including Noncontrolling Interest
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax		11		(173)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax		(10)	[1]	167	[2]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax		(2)	[3]	17	[4]
Other Comprehensive Income (Loss), Net of Tax		(12)		184
Adoption of New Accounting Standard_Reclass from AOCI to Retained Earnings	[5]			0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest		0		0
Accumulated Other Comprehensive Income (Loss), Net of Tax		(1)		11		(173)
Other Comprehensive Income (Loss) before Reclassifications, Tax		(1)		0
Reclassification from AOCI, Current Period, Tax		0		0
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Including Portion Attributable to Noncontrolling Interest
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax		(4,198)		(4,058)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax		(453)	[1]	(43)	[2]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax		303	[3]	212	[4]
Other Comprehensive Income (Loss), Net of Tax		(150)		169
Adoption of New Accounting Standard_Reclass from AOCI to Retained Earnings	[5]			(308)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest		2		1
Accumulated Other Comprehensive Income (Loss), Net of Tax		(4,350)		(4,198)		(4,058)
Other Comprehensive Income (Loss) before Reclassifications, Tax		(131)		(44)
Reclassification from AOCI, Current Period, Tax		89		66
Accumulated Foreign Currency Adjustment Including Portion Attributable to Noncontrolling Interest
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax		(10,749)		(10,518)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax		(1,083)	[1]	(213)	[2]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax		0	[3]	0	[4]
Other Comprehensive Income (Loss), Net of Tax		(1,083)		(213)
Adoption of New Accounting Standard_Reclass from AOCI to Retained Earnings	[5]			(18)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest		(18)		0
Accumulated Other Comprehensive Income (Loss), Net of Tax		(11,814)		(10,749)		$ (10,518)
Accumulated Other Comprehensive Income (Loss), Derivative Qualifying as Hedge, Excluded Component, Including Portion Attributable to Noncontrolling Interest [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Other Comprehensive Income (Loss) before Reclassifications, Tax		59		78
Reclassification from AOCI, Current Period, Tax		$ 0		$ 0

[1] Net of tax (benefit)/expense of $(1), $(131) and $59 for gains/losses on investment securities, postretirement benefit items and foreign currency translation, respectively, for the period ended June 30, 2020.

[2] Net of tax benefit)/expense of $0, $(44) and $78 for gains/losses on investment securities, postretirement benefit items and foreign currency translation, respectively, for the period ended June 30, 2019.

[3] Net of tax (benefit)/expense of $0, $89 and $0 for gains/losses on investment securities, postretirement benefit items and foreign currency translation, respectively, for the period ended June 30, 2020.

[4] Net of tax (benefit)/expense of $0, $66 and $0 for gains/losses on investment securities, postretirement benefit items and foreign currency translation, respectively, for the period ended June 30, 2019.

[5] Adjustment made to early adopt ASU 2018-02: "Reclassification of Certain Effects from Accumulated Other Comprehensive Income."