Basis of Presentation and Significant Accounting Policies Narrative (Details)				3 Months Ended									12 Months Ended
	Feb. 07, 2019	Nov. 30, 2018 USD ($) $ / shares	Aug. 09, 2018 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($) television_station	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2018 USD ($) television_station		Dec. 31, 2017 USD ($)		Dec. 31, 2016 USD ($)		May 08, 2018 USD ($) television_station
Summary of Significant Account Policies [Line Items]
Number of Television Stations | television_station					42								42
Total operating revenues					$ 578,733,000	$ 498,008,000	$ 489,358,000	$ 443,635,000	$ 488,999,000	$ 450,533,000	$ 469,517,000	$ 439,910,000	$ 2,009,734,000	[1]	$ 1,848,959,000	[1]	$ 1,947,930,000	[1]
Costs and Expenses													1,521,294,000		1,763,306,000		1,539,158,000
Program Rights Obligations					465,962,000				554,000,000				465,962,000		554,000,000
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification					14,000,000										23,000,000		25,000,000
Restricted cash and cash equivalents					16,607,000				17,566,000				$ 16,607,000		17,566,000		17,566,000
Deferred Revenue and Other LT Liability, Useful Lives, Spectrum													30 years
Broadcast rights impairment charge													$ 28,000,000		80,000,000		37,000,000
Advertising Expense													36,000,000		34,000,000		42,000,000
Self-insurance deductible, per occurrence					1,000,000								1,000,000
Liabilities for self-insured risks					23,000,000				24,000,000				23,000,000		24,000,000
Deferred Rent Credit					18,000,000								18,000,000
Scenario, Forecast
Summary of Significant Account Policies [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification				$ 13,000,000
Minimum
Summary of Significant Account Policies [Line Items]
Increase In Assets Due to Lease Accounting Implementation					150,000,000								150,000,000
Increase in Liabilities Due to Lease Accounting Implementation					165,000,000								$ 165,000,000
Minimum | Buildings
Summary of Significant Account Policies [Line Items]
Useful life of property, plant and equipment, years													2 years
Minimum | Equipment
Summary of Significant Account Policies [Line Items]
Useful life of property, plant and equipment, years													3 years
Maximum
Summary of Significant Account Policies [Line Items]
Increase In Assets Due to Lease Accounting Implementation					165,000,000								$ 165,000,000
Increase in Liabilities Due to Lease Accounting Implementation					180,000,000								$ 180,000,000
Maximum | Buildings
Summary of Significant Account Policies [Line Items]
Useful life of property, plant and equipment, years													44 years
Maximum | Equipment
Summary of Significant Account Policies [Line Items]
Useful life of property, plant and equipment, years													30 years
Corporate, Non-Segment
Summary of Significant Account Policies [Line Items]
Total operating revenues					1,793,000	$ 3,389,000	$ 2,941,000	$ 2,933,000	2,977,000	$ 3,226,000	$ 3,456,000	$ 3,877,000	$ 11,056,000	[1]	13,536,000	[1]	38,034,000	[1]
Restricted cash and cash equivalents					17,000,000				18,000,000				17,000,000		18,000,000
Barter
Summary of Significant Account Policies [Line Items]
Total operating revenues													28,000,000		28,000,000		30,000,000
Costs and Expenses													28,000,000		28,000,000		$ 30,000,000
Program rights					44,000,000				45,000,000				44,000,000		45,000,000
Program Rights Obligations					$ 44,000,000				$ 45,000,000				$ 44,000,000		$ 45,000,000
Subsequent Event
Summary of Significant Account Policies [Line Items]
Hart-Scott-Rodino Antitrust Improvement Act of 1976 Waiting Period	30 days
Nexstar Merger
Summary of Significant Account Policies [Line Items]
Business Acquisition, Share Price | $ / shares		$ 46.50
Business Acquisition, Share Price, Daily Price Increase After Target Close Date		$ 0.009863
Contract Termination Fee		135,000,000
Contract Termination Fees Nexstar Cost Reimbursement		15,000,000
Contract Termination Fee When Stockholder Merger Vote Not Obtained		$ 15,000,000
Sinclair Merger | Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations
Summary of Significant Account Policies [Line Items]
Television stations, To sell upon close of merger | television_station																			7
Disposal Group, Including Discontinued Operation, Consideration																			$ 910,000,000
Fox Purchase Agreement
Summary of Significant Account Policies [Line Items]
Contract Termination Fee			$ 0

[1] (1)See Note 2 for the disclosures of operating revenues and operating loss included in discontinued operations for the historical periods.