Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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Stock Compensation Plans - Narrative (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 7	$ 8	$ 11	$ 14
Unearned compensation cost related to the unvested portion of all stock-based awards	$ 26		$ 26
Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Equity instruments granted (shares)			0.6
Weighted average fair value per share granted (dollars per share)			$ 16.34
Performance Share Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Equity instruments granted (shares)			0.1
Weighted average fair value per share granted (dollars per share)			$ 19.21