Stock-Based Compensation - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation expense	$ 6	$ 4	$ 14	$ 9
2017 ESPP \| Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation shares authorized (in shares)	800,000		800,000
Shares available for issuance (in shares)	382,140		382,140
Shares issued during period (in shares)	43,946		149,789

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

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