Accounting Pronouncements (Details) $ in Millions	Dec. 31, 2019 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease assets (Note 17)	$ 1,812
Operating lease liabilities (Note 17)	$ 1,471
Minimum [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Finance lease, renewal term	12 months
Operating lease, renewal term	12 months
ASU 2016-02 Adopted [Member] | Assets, Total [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease liabilities (Note 17)	$ 2,000
ASU 2016-02 Adopted [Member] | Liabilities, Total [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease assets (Note 17)	$ 2,000
ASU 2016-02 Adopted [Member] | Minimum [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Finance lease, renewal term	12 months
Operating lease, renewal term	12 months