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Fair Value Measurements - Additional Information (Detail) - USD ($)	3 Months Ended				9 Months Ended		12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Impaired Long Lived Assets Held And Used [Line Items]
Impairment of long-lived assets					$ 17,200,000
Impairment of equity method investment	$ 17,145,000			$ 17,000,000	17,245,000	$ 17,000,000
Payments to acquire ownership interest					2,750,000
Impairment charges of the indefinite-lived trademarks	4,814,000				23,709,000
Trademarks
Impaired Long Lived Assets Held And Used [Line Items]
Impairment charges of the indefinite-lived trademarks	$ 4,800,000	$ 5,200,000	$ 13,700,000	$ 0	$ 23,700,000	$ 0
MG Icon
Impaired Long Lived Assets Held And Used [Line Items]
Impairment of equity method investment							$ 9,600,000
Payments to acquire ownership interest							2,600,000
Marcy Media Holdings
Impaired Long Lived Assets Held And Used [Line Items]
Impairment of equity method investment							$ 17,000,000