FAIR VALUE OF FINANCIAL INSTRUMENTS - Valuation Techniques on Fair Value Measurements (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Disclosure Of Significant Unobservable Inputs Used In Fair Value Measurements Of Assets And Liabilities [Table] [Line Items]
Financial assets	$ 43,268	$ 41,335
Financial liabilities	(201,673)	(197,540)
Level 2
Disclosure Of Significant Unobservable Inputs Used In Fair Value Measurements Of Assets And Liabilities [Table] [Line Items]
Financial assets	7,932	8,520
Financial liabilities	(5,162)	(5,167)
Level 2 | Accounts payable and other
Disclosure Of Significant Unobservable Inputs Used In Fair Value Measurements Of Assets And Liabilities [Table] [Line Items]
Financial liabilities	(5,076)	(5,090)
Level 2 | Accounts payable and other | Discounted cash flows
Disclosure Of Significant Unobservable Inputs Used In Fair Value Measurements Of Assets And Liabilities [Table] [Line Items]
Financial liabilities	(5,076)
Level 2 | Redeemable fund units (subsidiary equity obligations)
Disclosure Of Significant Unobservable Inputs Used In Fair Value Measurements Of Assets And Liabilities [Table] [Line Items]
Financial liabilities	(86)	(77)
Level 2 | Redeemable fund units (subsidiary equity obligations) | Market approach
Disclosure Of Significant Unobservable Inputs Used In Fair Value Measurements Of Assets And Liabilities [Table] [Line Items]
Financial liabilities	(86)
Level 2 | Accounts receivable and other
Disclosure Of Significant Unobservable Inputs Used In Fair Value Measurements Of Assets And Liabilities [Table] [Line Items]
Financial assets	1,803	1,581
Level 2 | Other financial assets | Market approach
Disclosure Of Significant Unobservable Inputs Used In Fair Value Measurements Of Assets And Liabilities [Table] [Line Items]
Financial assets	6,129
Level 2 | Fixed income securities and other
Disclosure Of Significant Unobservable Inputs Used In Fair Value Measurements Of Assets And Liabilities [Table] [Line Items]
Financial assets	1,212	912
Level 2 | Corporate bonds
Disclosure Of Significant Unobservable Inputs Used In Fair Value Measurements Of Assets And Liabilities [Table] [Line Items]
Financial assets	2,042	2,764
Level 2 | Common shares and warrants
Disclosure Of Significant Unobservable Inputs Used In Fair Value Measurements Of Assets And Liabilities [Table] [Line Items]
Financial assets	742	577
Level 3
Disclosure Of Significant Unobservable Inputs Used In Fair Value Measurements Of Assets And Liabilities [Table] [Line Items]
Financial assets	2,257	2,369
Financial liabilities	(2,072)	(2,104)
Level 3 | Accounts payable and other
Disclosure Of Significant Unobservable Inputs Used In Fair Value Measurements Of Assets And Liabilities [Table] [Line Items]
Financial liabilities	(689)	(724)
Level 3 | Accounts payable and other | Discounted cash flows
Disclosure Of Significant Unobservable Inputs Used In Fair Value Measurements Of Assets And Liabilities [Table] [Line Items]
Financial liabilities	(689)
Level 3 | Redeemable fund units (subsidiary equity obligations)
Disclosure Of Significant Unobservable Inputs Used In Fair Value Measurements Of Assets And Liabilities [Table] [Line Items]
Financial liabilities	(1,383)	(1,380)
Level 3 | Redeemable fund units (subsidiary equity obligations) | Discounted cash flows
Disclosure Of Significant Unobservable Inputs Used In Fair Value Measurements Of Assets And Liabilities [Table] [Line Items]
Financial liabilities	(1,383)
Level 3 | Accounts receivable and other
Disclosure Of Significant Unobservable Inputs Used In Fair Value Measurements Of Assets And Liabilities [Table] [Line Items]
Financial assets	89	135
Level 3 | Fixed income securities and other
Disclosure Of Significant Unobservable Inputs Used In Fair Value Measurements Of Assets And Liabilities [Table] [Line Items]
Financial assets	562	491
Level 3 | Fixed income securities and other | Discounted cash flows
Disclosure Of Significant Unobservable Inputs Used In Fair Value Measurements Of Assets And Liabilities [Table] [Line Items]
Financial assets	562
Level 3 | Corporate bonds
Disclosure Of Significant Unobservable Inputs Used In Fair Value Measurements Of Assets And Liabilities [Table] [Line Items]
Financial assets		286
Level 3 | Corporate bonds | Discounted cash flows
Disclosure Of Significant Unobservable Inputs Used In Fair Value Measurements Of Assets And Liabilities [Table] [Line Items]
Financial assets	402
Level 3 | Common shares and warrants
Disclosure Of Significant Unobservable Inputs Used In Fair Value Measurements Of Assets And Liabilities [Table] [Line Items]
Financial assets	1,184	$ 1,389
Level 3 | Common shares and warrants | Black-Scholes model
Disclosure Of Significant Unobservable Inputs Used In Fair Value Measurements Of Assets And Liabilities [Table] [Line Items]
Financial assets	1,184
Level 3 | Accounts receivable and other | Discounted cash flows
Disclosure Of Significant Unobservable Inputs Used In Fair Value Measurements Of Assets And Liabilities [Table] [Line Items]
Financial assets	$ 89