Note 2 - Acquisitions and Dispositions (Details Textual) - USD ($)												12 Months Ended
	Aug. 01, 2017	Jun. 01, 2017	May 01, 2017	Jan. 17, 2017	Jan. 13, 2017	Jun. 27, 2016	Jun. 01, 2016	Feb. 16, 2016	Feb. 01, 2016	Sep. 01, 2015	Jul. 02, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Combination, Consideration Transferred													$ 473,074,000
Goodwill												$ 611,100,000	485,318,000	$ 423,236,000
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual												79,800,000	130,400,000
Business Acquisition, Pro Forma Income (Loss) from Continuing Operations, Net of Tax												33,700,000	55,800,000
Business Combination, Acquisition Related Costs												1,100,000	7,400,000
Proceeds from Divestiture of Businesses												0	11,200,000	0
Long-term Debt												1,800,000,000	1,800,000,000
Finite-lived Intangible Assets Acquired												42,606,000	19,566,000
Goodwill, Acquired During Period												125,782,000	72,296,000	48,300,000
2016 Term Loan [Member]
Long-term Debt								$ 425,000,000
KAKE-TV [Member]
Business Combination, Consideration Transferred									$ 443,100,000				0
Proceeds from Divestiture of Businesses									11,200,000				11,200,000
Gain (Loss) on Disposition of Business									$ 2,000,000
Helena Montana Disposition [Member]
Gain (Loss) on Disposition of Assets										$ 100,000
NBC Affiliate and Television Station KTVH-TV [Member]
Gain (Loss) on Disposition of Assets														900,000
Disposal Group, Including Discontinued Operation, Consideration														3,000,000
Fairbanks Acquistion [Member]
Payments to Acquire Businesses, Gross					$ 8,000,000
Goodwill												471,000
Green Bay Acquisition and Davenport Acquisition [Member]
Business Combination, Consideration Transferred				$ 269,900,000
Clarksburg Acquisition [Member]
Payments to Acquire Businesses, Gross							$ 16,500,000
Business Combination, Consideration Transferred			$ 26,500,000
Goodwill												3,222,000
Bangor Acquisition and Gainesville Acquisition [Member]
Business Combination, Consideration Transferred			$ 85,000,000
Burlington and Plattsburg Acquisition [Member]
Payments to Acquire Businesses, Gross	$ 5,800,000	$ 23,200,000
Business Combination, Consideration Transferred	$ 29,000,000
2017 Acquisitions [Member]
Goodwill												125,782,000
2017 Acquisitions [Member] | Retransmission Agreements [Member]
Finite-Lived Intangible Assets, Gross												$ 27,900,000
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life												5 years 36 days
2017 Acquisitions [Member] | Advertising Relationships [Member]
Finite-Lived Intangible Assets, Gross												$ 5,300,000
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life												10 years 255 days
2017 Acquisitions [Member] | Income Leases [Member]
Finite-Lived Intangible Assets, Gross												$ 3,000,000
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life												11 years 328 days
2017 Acquisitions [Member] | Minimum [Member]
Property, Plant and Equipment, Useful Life												3 years
2017 Acquisitions [Member] | Maximum [Member]
Property, Plant and Equipment, Useful Life												40 years
Schurz Acquisition [Member]
Proceeds from Divestiture of Businesses								$ 16,000,000
KYES-TV Acquisition [Member]
Payments to Acquire Businesses, Gross						$ 500,000
Goodwill													28,000
WBXX Acquisition [Member]
Business Combination, Consideration Transferred													30,000,000
Goodwill													10,288,000
Proceeds from Divestiture of Businesses													0
Accounts Receivable Contractual Amounts in Excess of Fair Value													$ 200,000
Schurz Acquisition and Related Transaction [Member] | Retransmission Agreements [Member]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life													4 years 328 days
Finite-lived Intangible Assets Acquired													$ 14,900,000
Schurz Acquisition and Related Transaction [Member] | Advertising Relationships [Member]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life													5 years 182 days
Finite-lived Intangible Assets Acquired													$ 1,600,000
Schurz Acquisition and Related Transaction [Member] | Off-Market Favorable Lease [Member]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life													9 years 182 days
Finite-lived Intangible Assets Acquired													$ 2,600,000
Schurz Acquisition and Related Transaction [Member] | Minimum [Member]
Property, Plant and Equipment, Useful Life													3 years
Schurz Acquisition and Related Transaction [Member] | Maximum [Member]
Property, Plant and Equipment, Useful Life													40 years
Cedar Rapids [Member]
Business Combination, Consideration Transferred										$ 100,000,000
Goodwill														25,006,000
Odessa [Member]
Business Combination, Consideration Transferred											$ 33,600,000
Goodwill														3,719,000
Twin Falls [Member]
Business Combination, Consideration Transferred											17,500,000
Goodwill														2,587,000
Wausau [Member]
Business Combination, Consideration Transferred											14,000,000
Goodwill														11,616,000
Presque Isle [Member]
Business Combination, Consideration Transferred											10,300,000
Goodwill														245,000
Laredo [Member]
Business Combination, Consideration Transferred											$ 9,000,000
Goodwill														5,154,000
The 2015 Acquisitions [Member]
Goodwill														48,327,000
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual														23,200,000
Business Acquisition, Pro Forma Income (Loss) from Continuing Operations, Net of Tax														8,600,000
The 2015 Acquisitions [Member] | General and Administrative Expense [Member]
Business Combination, Acquisition Related Costs														$ 6,500,000
The 2015 Acquisitions [Member] | Retransmission Agreements [Member]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life														5 years 109 days
Finite-lived Intangible Assets Acquired														$ 9,700,000
The 2015 Acquisitions [Member] | Advertising Relationships [Member]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life														9 years 219 days
Finite-lived Intangible Assets Acquired														$ 1,000,000
The 2015 Acquisitions [Member] | Income Leases [Member]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life														16 years 328 days
Finite-lived Intangible Assets Acquired														$ 5,400,000
The 2015 Acquisitions [Member] | Minimum [Member]
Property, Plant and Equipment, Useful Life														3 years
The 2015 Acquisitions [Member] | Maximum [Member]
Property, Plant and Equipment, Useful Life														40 years