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Basis of Presentation - Narrative (Details) - USD ($)
$ in Millions
3 Months Ended 12 Months Ended
Mar. 31, 2017
Mar. 31, 2016
Dec. 31, 2016
Concentration Risk [Line Items]      
Unrealized losses on available for sales investments recognized in comprehensive income $ 2.3 $ 2.0  
Revenue | Media      
Concentration Risk [Line Items]      
Percentage of revenue not expected to have material change     90.00%
Television Advertising Revenue | Revenue | Media      
Concentration Risk [Line Items]      
Concentration risk (as a percent)     60.00%
Retransmission Revenue | Revenue | Media      
Concentration Risk [Line Items]      
Concentration risk (as a percent)     30.00%