Supplemental Cash Flow Information - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Supplemental Cash Flow Information [Abstract]
Transfer from investments	$ 14	$ 20
Non-cash financing activities related to the issuance of shares for vested restricted stock units	50	51
Operating lease, payments	46	39
ROU asset obtained in exchange for operating lease liability	$ 103	$ 31