Summary of Ownership Structure and Ownership Percentage of Non-consolidated Investments (Detail)	Dec. 31, 2017
MPEG LA
Schedule of Equity Method Investments [Line Items]
Equity method ownership, percentage	8.40%
Music Choice
Schedule of Equity Method Investments [Line Items]
Equity method ownership, percentage	18.20%
Conditional Access Licensing ("CAL")
Schedule of Equity Method Investments [Line Items]
Equity method ownership, percentage	49.00%
Combined Conditional Access Development ("CCAD")
Schedule of Equity Method Investments [Line Items]
Equity method ownership, percentage	50.00%