Business operations and segment information - Narrative (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($) market station segment	Dec. 28, 2014 USD ($)	Dec. 29, 2013 USD ($)
Segment Reporting Information [Line Items]
Number of operating segments | segment	2
Number of television stations | station	46
Number of markets In which entity operates | market	38
Revenues	$ 3,050,945	$ 2,626,141	$ 1,603,123
Foreign Countries
Segment Reporting Information [Line Items]
Revenues	76,000	75,800	62,300
Long-lived assets	$ 213,800	205,000
Media
Segment Reporting Information [Line Items]
Number of television stations | station	46
Number of markets In which entity operates | market	38
Operating Segments
Segment Reporting Information [Line Items]
Assets of discontinued operations	$ 7,000	2,400,000
Operating Segments | Media
Segment Reporting Information [Line Items]
Revenues	$ 1,682,144	$ 1,691,866	$ 835,113