v3.19.3.a.u2
Accumulated Other Comprehensive Income (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Defined Benefit Plans, Beginning Balance $ (361) $ (400) $ (547)
Other Comprehensive Income (Loss), Defined Benefit Plans (51) (39) (147)
Defined Benefit Plans, Ending Balance (350) (361) (400)
Net Unrealized Gain on Securities, Beginning Balance 0 (58)  
Unrealized loss on securities, net of tax 0 0 (58)
Net Unrealized Gain on Securities, Ending Balance 0 0 (58)
Foreign Currency Translation, Beginning Balance (5,702) (5,060) (5,646)
Other comprehensive income (loss), Foreign Currency Translation 695 (642) 586
Foreign Currency Translation, Ending Balance (5,007) (5,702) (5,060)
Accumulated Other Comprehensive Income (loss), Beginning Balance (6,063) (5,518) (6,193)
Other comprehensive income (loss), net of tax 746 (603) 675
Accumulated Other Comprehensive Income (loss), Ending Balance (5,357) (6,063) $ (5,518)
ASU 2016-01 Accounting for Cenovus Shares [Member] | Restatement Adjustment [Member]      
Other comprehensive income (loss), net of tax   $ 58  
ASU 2018-02 [Member]      
Other Comprehensive Income (Loss), Defined Benefit Plans 40    
Other comprehensive income (loss), net of tax $ (40)