Summary of Significant Accounting Policies - Subsequent Events - Narrative (Details) - Subsequent Event - ATi $ in Millions	Jan. 01, 2021 USD ($)
Business Acquisition [Line Items]
Outstanding common stock acquired (as a percent)	100.00%
Total purchase consideration, net of cash acquired	$ 44

Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 8
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
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