POSTRETIREMENT BENEFITS AND EMPLOYEE STOCK OWNERSHIP PLAN - FAIR VALUE OF PLAN ASSETS (Details) RETAG - USD ($) $ in Millions		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2018
Pension Plan
ASSETS AT FAIR VALUE
Defined Benefit Plan, Plan Assets, Amount	[1]	$ 11,484	$ 11,382	$ 11,267
Pension Plan | Fair Value, Inputs, Level 1, 2 and 3 [Member]
ASSETS AT FAIR VALUE
Defined Benefit Plan, Plan Assets, Amount		2,167	425
Pension Plan | Cash and Cash Equivalents | Fair Value, Inputs, Level 1
ASSETS AT FAIR VALUE
Defined Benefit Plan, Plan Assets, Amount		61	47
Pension Plan | Company Stock | Fair Value, Inputs, Level 1
ASSETS AT FAIR VALUE
Defined Benefit Plan, Plan Assets, Amount		0	0
Pension Plan | Company Preferred Stock | Fair Value, Inputs, Level 2
ASSETS AT FAIR VALUE
Defined Benefit Plan, Plan Assets, Amount	[2]	0	0
Pension Plan | Fixed Income Securities | Fair Value, Inputs, Level 2
ASSETS AT FAIR VALUE
Defined Benefit Plan, Plan Assets, Amount	[3]	1,991	265
Pension Plan | Insurance Contracts [Domain] | Fair Value, Inputs, Level 3
ASSETS AT FAIR VALUE
Defined Benefit Plan, Plan Assets, Amount	[4]	115	113
Pension Plan | Other Assets | Fair Value Measured at Net Asset Value Per Share [Member]
ASSETS AT FAIR VALUE
Defined Benefit Plan, Plan Assets, Amount	[5]	9,317	10,957
Other Retiree Benefits
ASSETS AT FAIR VALUE
Defined Benefit Plan, Plan Assets, Amount	[6]	5,618	5,096	$ 3,259
Other Retiree Benefits | Fair Value, Inputs, Level 1, 2 and 3 [Member]
ASSETS AT FAIR VALUE
Defined Benefit Plan, Plan Assets, Amount		5,489	4,948
Other Retiree Benefits | Cash and Cash Equivalents | Fair Value, Inputs, Level 1
ASSETS AT FAIR VALUE
Defined Benefit Plan, Plan Assets, Amount		121	111
Other Retiree Benefits | Company Stock | Fair Value, Inputs, Level 1
ASSETS AT FAIR VALUE
Defined Benefit Plan, Plan Assets, Amount		217	179
Other Retiree Benefits | Company Preferred Stock | Fair Value, Inputs, Level 2
ASSETS AT FAIR VALUE
Defined Benefit Plan, Plan Assets, Amount	[2]	5,139	4,657
Other Retiree Benefits | Fixed Income Securities | Fair Value, Inputs, Level 2
ASSETS AT FAIR VALUE
Defined Benefit Plan, Plan Assets, Amount	[3]	12	1
Other Retiree Benefits | Insurance Contracts [Domain] | Fair Value, Inputs, Level 3
ASSETS AT FAIR VALUE
Defined Benefit Plan, Plan Assets, Amount	[4]	0	0
Other Retiree Benefits | Other Assets | Fair Value Measured at Net Asset Value Per Share [Member]
ASSETS AT FAIR VALUE
Defined Benefit Plan, Plan Assets, Amount	[5]	$ 129	$ 148

[1] Primarily non-U.S.-based defined benefit retirement plans.

[2] Company preferred stock is valued based on the value of Company common stock and is presented net of ESOP debt discussed below.

[3] Fixed income securities, classified as Level 2, are estimated by using pricing models or quoted prices of securities with similar characteristics.

[4] Fair values of insurance contracts are valued based on either their cash equivalent value or models that project future cash flows and discount the future amounts to a present value using market-based observable inputs, including credit risk and interest rate curves. The activity for Level 3 assets is not significant for all years presented.

[5] Investments valued using net asset value as a practical expedient are primarily equity and fixed income collective funds.

[6] Primarily U.S.-based other postretirement benefit plans.