Goodwill and Identifiable Intangible Assets - Narrative (Details) - USD ($)	5 Months Ended	12 Months Ended
Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Goodwill [Line Items]
Goodwill impairment	$ 10,700,000	$ 0	$ 10,718,000	$ 0
Amortization expense		8,000,000.0	$ 7,700,000	$ 11,700,000
MCM And Cabot
Goodwill [Line Items]
Goodwill impairment		$ 0

Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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