Business operations and segment information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Operating revenues	$ 2,207,282	$ 1,903,026	$ 2,004,088
Operating income	698,476	545,902	708,152
Depreciation, amortization, asset impairment and other (gains) charges	75,086	81,067	110,762
Capital expenditures	65,230	39,445	43,215
Operating Segments | Media
Segment Reporting Information [Line Items]
Operating revenues	2,207,282	1,903,026	1,994,120
Operating income	752,292	602,514	800,791
Depreciation, amortization, asset impairment and other (gains) charges	73,737	79,398	85,890
Capital expenditures	62,141	39,055	41,572
Operating Segments | Digital
Segment Reporting Information [Line Items]
Operating revenues	0	0	9,968
Operating income	0	0	(30,241)
Depreciation, amortization, asset impairment and other (gains) charges	0	0	21,166
Capital expenditures	0	0	0
Corporate
Segment Reporting Information [Line Items]
Operating income	(53,816)	(56,612)	(62,398)
Depreciation, amortization, asset impairment and other (gains) charges	1,349	1,669	3,706
Capital expenditures	$ 3,089	$ 390	$ 1,643