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SUPPLEMENTAL CASH FLOW INFORMATION (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Cash Flow Statement [Abstract]      
Interest paid $ 985 $ 829 $ 507
Income taxes paid 172 179 427
Changes in non-cash working capital      
Accounts receivable 284 42 176
Prepayments (415) (120) 5
Accounts payable and other (89) 146 (305)
Changes in non-cash working capital, net $ (220) $ 68 $ (124)