Fair Value Measurements - Additional Information (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Goodwill impairment		$ 51,200,000	$ 0	$ 0
Impairment of intangible assets				$ 0
Impairment of intangible assets including goodwill		55,000,000	$ 2,200,000
Cloud Tv Reporting Unit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Goodwill impairment	$ 51,200,000	51,200,000
Cloud Tv Reporting Unit | Trade Names [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment of intangible assets	3,800,000	3,800,000
Non-controlling Interest | Cloud Tv Reporting Unit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Goodwill impairment	17,900,000	17,900,000
Impairment of intangible assets including goodwill		$ 19,300,000
Non-controlling Interest | Cloud Tv Reporting Unit | Trade Names [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment of intangible assets	$ 1,300,000