Description of business, basis of presentation and summary of significant accounting policies - Additional Information (Detail)	3 Months Ended	12 Months Ended
	Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($) segment market station $ / shares	Dec. 31, 2015 USD ($)	Dec. 28, 2014 USD ($)	Sep. 07, 2016
Significant Accounting Policies [Line Items]
Number of television stations | station		46
Number of markets In which entity operates | market		38
Additional days in 2015 fiscal period		2 days		4 days
Redeemable noncontrolling interest		$ 46,300,000	$ 24,700,000
Number of operating segments | segment		2
Write-offs of accounts receivable		$ 8,500,000	6,000,000	$ 4,300,000
Non-cash goodwill impairment charge		15,218,000	8,000,000	$ 30,300,000
Impairment of indefinite-lived intangible assets		$ 0
Retransmission consent revenue (as a percent of total revenue)		30.00%		27.00%
Debt issuance costs		$ 27,615,000	31,800,000
Provision for income taxes		$ 216,979,000	$ 202,314,000	$ 234,471,000
Effective tax rate (as a percent)		32.80%	36.10%	25.40%
Unrealized (losses) gains on available for sale investment during the period		$ (11,346,000)	$ 3,311,000	$ 0
Media
Significant Accounting Policies [Line Items]
Number of television stations | station		46
Digital
Significant Accounting Policies [Line Items]
Non-cash goodwill impairment charge	$ 15,200,000	$ 15,218,000	8,000,000
Other
Significant Accounting Policies [Line Items]
Investments in non-public businesses, non-operating expense		$ 21,800,000	8,600,000
Minimum
Significant Accounting Policies [Line Items]
Term of SaaS contract		2 years
Maximum
Significant Accounting Policies [Line Items]
Term of SaaS contract		3 years
Building and Building Improvements | Minimum
Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life (in years)		10 years
Building and Building Improvements | Maximum
Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life (in years)		40 years
Machinery and Equipment | Minimum
Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life (in years)		3 years
Machinery and Equipment | Maximum
Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life (in years)		25 years
Restricted Stock
Significant Accounting Policies [Line Items]
Requisite service period		4 years
Performance Shares
Significant Accounting Policies [Line Items]
Requisite service period		3 years
Career Builder
Significant Accounting Policies [Line Items]
Percentage of ownership interests in subsidiary (as a percent)		47.00%			53.00%
Cost of Sales
Significant Accounting Policies [Line Items]
Bad debt expense		$ 11,300,000	6,900,000	4,100,000
Selling, General and Administrative Expenses
Significant Accounting Policies [Line Items]
Advertising costs		161,300,000	173,300,000	110,100,000
PointRoll | Digital
Significant Accounting Policies [Line Items]
Non-cash goodwill impairment charge	15,200,000
Operating Segments | Digital
Significant Accounting Policies [Line Items]
Non-cash goodwill impairment charge	$ 15,200,000	$ 15,218,000	$ 8,000,000	$ 30,271,000
Advertising Revenue | Sales Revenue | Operating Segments | Media
Significant Accounting Policies [Line Items]
Concentration risk (as a percent)		60.00%
Retransmission Revenue | Sales Revenue | Operating Segments | Media
Significant Accounting Policies [Line Items]
Concentration risk (as a percent)		30.00%
New Accounting Pronouncement, Early Adoption, Effect | Accounting Standards Update 2016-09
Significant Accounting Policies [Line Items]
Provision for income taxes		$ (6,400,000)
Effective tax rate (as a percent)		(1.00%)
Increase to basic and diluted earnings per share (in dollars per share) | $ / shares		$ 0.03