Supplemental Cash Flow Information - Narrative (Details) - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2021	Jun. 30, 2020
Supplemental Cash Flow Information [Abstract]
Transfer from investments	$ 15	$ 21
Non-cash financing activities related to the issuance of shares for vested restricted stock units	51	56
Operating lease, payments	91	78
ROU asset obtained in exchange for operating lease liability	$ 92	$ 52

Amount of cash outflow from operating lease, excluding payments to bring another asset to condition and location necessary for its intended use.

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-Name Accounting Standards Codification
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Amount of increase in right-of-use asset obtained in exchange for operating lease liability.

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Value of stock issued during the period upon the conversion of units. An example of a convertible unit is an umbrella partnership real estate investment trust unit (UPREIT unit).

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Value of investments transferred from the entity's investments in noncash transactions.

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