Shareholders' Equity - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense related to stock incentive plans	$ 5	$ 5
Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Common Stock, shares issued (shares)	207,020
Restricted Common Stock, fair value per share (USD per share)	$ 111.13

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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
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-Section 50
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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