Supplemental Cash Flow Information - Narrative (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Supplemental Cash Flow Information [Abstract]
Transfer from investments	$ 31	$ 42
Non-cash financing activities related to the issuance of shares for vested restricted stock units	52	56
Operating lease, payments	137	118
ROU asset obtained in exchange for operating lease liability	$ 96	$ 47