Goodwill and Identifiable Intangible Assets - Significant Assumptions Used to Estimate the Fair Values of Tradenames Impaired (Parenthetical) (Detail) - Long-term Revenue Growth Rates [Member]	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Long-term revenue growth rate projection period	10 years	10 years
Alternative Investment Type Extensible List	us-gaap:TradeNamesMember	us-gaap:TradeNamesMember

Indicates type of alternative investment.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

Name:	us-gaap_AlternativeInvestmentTypeExtensibleList
Namespace Prefix:	us-gaap_
Data Type:	srt-types:extensibleListItemType
Balance Type:	na
Period Type:	instant