Investments Equity Method Investments (Details) - USD ($) $ in Thousands	3 Months Ended			12 Months Ended
	Mar. 31, 2018	Sep. 30, 2017	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2012
Schedule of Equity Method Investments [Line Items]
Aggregate fair value of investments as of Effective Date					$ 2,224,000
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity	$ 673,000
Equity Method Investment, Net Intangible Assets Subject to Amortization of Basis Difference, Useful Life	15 years
Equity method investments	$ 1,178,192			$ 1,254,198
Income on equity investments, net	39,137		$ 37,037
Distributions from equity investment	115,137		111,509
Write-down of investment	0		122,000
Sale of partial interest of equity method investment	833		0
Gain on investment transactions	$ 3,888		4,950
Television Food Network, G.P.
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	31.00%
Equity method investments	$ 1,158,000			1,234,000
Income on equity investments, net	39,000		38,000
Distributions from equity investment	$ 115,000		112,000
CareerBuilder, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	6.00%
Equity method investments	$ 9,000			10,000
Income on equity investments, net	$ (300)		(300)
Distributions from equity investment		$ 16,000
Write-down of investment			$ 122,000	181,000
Sale of partial interest of equity method investment		$ 158,000
Gain on investment transactions				$ 4,000
Dose Media, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	25.00%
Equity method investments	$ 0
Revaluation of Assets
Schedule of Equity Method Investments [Line Items]
Fresh-Start Adjustment, Increase (Decrease), Investments					1,615,000
Fresh-Start Adjustment, Carrying Value of Equity Investees' Amortizable Intangible Assets					1,108,000
Fresh-Start Adjustment, Carrying Value of Equity Investees' Goodwill and Intangible Assets not Subject to Amortization					$ 507,000