FAIR VALUE OF FINANCIAL INSTRUMENTS - Fair Value Hierarchy Levels (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Disclosure of carrying value and fair value of assets and liabilities
Financial assets	$ 41,335	$ 33,281
Financial liabilities	197,540	187,156
Level 1
Disclosure of carrying value and fair value of assets and liabilities
Financial assets	5,664	2,386
Financial liabilities	75	93
Level 1 | Accounts payable and other
Disclosure of carrying value and fair value of assets and liabilities
Financial liabilities	75	93
Level 1 | Subsidiary equity obligations
Disclosure of carrying value and fair value of assets and liabilities
Financial liabilities	0	0
Level 1 | Government bonds
Disclosure of carrying value and fair value of assets and liabilities
Financial assets	7	0
Level 1 | Corporate bonds
Disclosure of carrying value and fair value of assets and liabilities
Financial assets	192	0
Level 1 | Fixed income securities and other
Disclosure of carrying value and fair value of assets and liabilities
Financial assets	867	419
Level 1 | Common shares and warrants
Disclosure of carrying value and fair value of assets and liabilities
Financial assets	4,548	1,966
Level 1 | Loans and notes receivables
Disclosure of carrying value and fair value of assets and liabilities
Financial assets	0	0
Level 1 | Accounts receivable and other
Disclosure of carrying value and fair value of assets and liabilities
Financial assets	50	1
Level 2
Disclosure of carrying value and fair value of assets and liabilities
Financial assets	8,520	8,145
Financial liabilities	5,167	3,789
Level 2 | Accounts payable and other
Disclosure of carrying value and fair value of assets and liabilities
Financial liabilities	5,090	3,749
Level 2 | Subsidiary equity obligations
Disclosure of carrying value and fair value of assets and liabilities
Financial liabilities	77	40
Level 2 | Government bonds
Disclosure of carrying value and fair value of assets and liabilities
Financial assets	2,644	2,403
Level 2 | Corporate bonds
Disclosure of carrying value and fair value of assets and liabilities
Financial assets	2,764	2,682
Level 2 | Fixed income securities and other
Disclosure of carrying value and fair value of assets and liabilities
Financial assets	912	851
Level 2 | Common shares and warrants
Disclosure of carrying value and fair value of assets and liabilities
Financial assets	577	421
Level 2 | Loans and notes receivables
Disclosure of carrying value and fair value of assets and liabilities
Financial assets	42	51
Level 2 | Accounts receivable and other
Disclosure of carrying value and fair value of assets and liabilities
Financial assets	1,581	1,737
Level 3
Disclosure of carrying value and fair value of assets and liabilities
Financial assets	2,369	1,780
Financial liabilities	2,104	2,542
Level 3 | Accounts payable and other
Disclosure of carrying value and fair value of assets and liabilities
Financial liabilities	724	686
Level 3 | Subsidiary equity obligations
Disclosure of carrying value and fair value of assets and liabilities
Financial liabilities	1,380	1,856
Level 3 | Government bonds
Disclosure of carrying value and fair value of assets and liabilities
Financial assets	0	0
Level 3 | Corporate bonds
Disclosure of carrying value and fair value of assets and liabilities
Financial assets		275
Level 3 | Fixed income securities and other
Disclosure of carrying value and fair value of assets and liabilities
Financial assets	491	480
Level 3 | Common shares and warrants
Disclosure of carrying value and fair value of assets and liabilities
Financial assets	1,389	802
Level 3 | Loans and notes receivables
Disclosure of carrying value and fair value of assets and liabilities
Financial assets	68	4
Level 3 | Accounts receivable and other
Disclosure of carrying value and fair value of assets and liabilities
Financial assets	$ 135	$ 219