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Goodwill and Identifiable Intangible Assets - Significant Assumptions Used to Estimate the Fair Values of Tradenames Impaired (Parenthetical) (Detail)
12 Months Ended
Dec. 31, 2020
Tradename [Member] | Long-term Revenue Growth Rate [Member]  
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]  
Long-term revenue growth rate projection period 10 years