Supplemental Cash Flow Information - Narrative (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Other Significant Noncash Transactions [Line Items]
Transfer from Investments	$ 46	$ 187
Non-cash financing activities related to the issuance of shares for vested restricted stock units	56	48
Operating lease, payments	118	115
ROU asset obtained in exchange for operating lease liability	$ 47	534
Accounting Standards Update 2016-02
Other Significant Noncash Transactions [Line Items]
ROU asset obtained in exchange for operating lease liability		$ 488