Real Estate Sales and Assets Held For Sale Narrative (Details) $ in Thousands																		3 Months Ended			12 Months Ended
		Dec. 19, 2017 USD ($)	Nov. 15, 2017 USD ($)	Aug. 04, 2017 USD ($)	May 22, 2017 USD ($) property	Apr. 21, 2017 USD ($) property	Jan. 31, 2017 USD ($) property	Jan. 26, 2017 USD ($)	Dec. 22, 2016 USD ($)	Nov. 14, 2016 USD ($)	Sep. 27, 2016 USD ($)	Sep. 26, 2016 USD ($)	Jul. 14, 2016 USD ($)	Jul. 12, 2016 USD ($) property	Jul. 07, 2016 USD ($)	Jun. 02, 2016 USD ($)	May 02, 2016 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2016 USD ($) property	Jun. 30, 2016 USD ($)	Dec. 31, 2017 USD ($) property	Dec. 31, 2016 USD ($) property	Dec. 31, 2015 USD ($)
Assets Held for Sale, Number of Properties Held for Sale | property																			5		0	5
Non-current assets held for sale	[1]																		$ 17,176		$ 38,900	$ 17,176
Impairment of Long-Lived Assets to be Disposed of																					2,000	15,000	$ 7,000
Proceeds from sales of real estate and other assets																					144,000	506,000	5,000
(Gain) loss on sale of real estate																			(1,000)	$ 1,000	(28,533)	(213,086)	97
(Distributions to) contributions from noncontrolling interests, net																					(9,251)	393	5,524
Proceeds from FCC spectrum auction																					172,102	0	$ 0
FCC licenses
Non-current assets held for sale																			$ 0		$ 38,900	$ 0
Subsequent Event | FCC licenses
Gain (Loss) on Disposition of Intangible Assets																		$ 133,000
Denver, CO Property
Proceeds from sales of real estate and other assets								$ 23,000
Chicago, IL Property
Proceeds from sales of real estate and other assets						$ 1,000	$ 22,000			$ 1,000
Sale Leaseback Transaction, Lease Terms							10
Gain (Loss) on Sale of Properties, Deferred							$ 13,000
Assets Held for Sale, Number of Properties Sold | property						2	1
Baltimore, MD Property
Proceeds from sales of real estate and other assets					$ 15,000				$ 300
Assets Held for Sale, Number of Properties Sold | property					2
Williamsburg, VA Property
Proceeds from sales of real estate and other assets				$ 1,000
Costa Mesa, CA Property
Proceeds from sales of real estate and other assets			$ 62,000
(Gain) loss on sale of real estate			(22,000)
Gain (Loss) on Sale of Properties, portion attributable to noncontrolling interest			$ 3,000
Fort Lauderdale, FL Property
Proceeds from sales of real estate and other assets		$ 21,000
(Gain) loss on sale of real estate		(6,000)
Gain (Loss) on Sale of Properties, portion attributable to noncontrolling interest		$ 100
Deerfield Beach Property
Proceeds from sales of real estate and other assets																	$ 24,000
Allentown Property
Proceeds from sales of real estate and other assets																$ 8,000
Seattle Property
Proceeds from sales of real estate and other assets															$ 19,000
Sale Leaseback Transaction, Lease Terms															11
Gain (Loss) on Sale of Properties, Deferred															$ 8,000
Orlando Sentinel Property
Proceeds from sales of real estate and other assets														$ 34,000
(Gain) loss on sale of real estate														$ (2,000)
Assets Held for Sale, Number of Properties Sold | property														2
Arlington Heights Property
Proceeds from sales of real estate and other assets													$ 400
Tribune Tower
Proceeds from sales of real estate and other assets												$ 199,000
(Gain) loss on sale of real estate												$ (93,000)
Sale of Real Estate, Contingency Period												5 years
Tribune Tower | Contingent Payment
Proceeds from sales of real estate and other assets												$ 35,000
LA Times Property
Proceeds from sales of real estate and other assets												102,000
(Gain) loss on sale of real estate												$ (59,000)
Sale of Real Estate, Contingency Period												5 years
LA Times Property | Contingent Payment
Proceeds from sales of real estate and other assets												$ 10,000
Olympic Property
Proceeds from sales of real estate and other assets											$ 118,000
(Gain) loss on sale of real estate											$ (59,000)

[1] (4)See Note 2 for information regarding discontinued operations and Note 6 for information regarding assets held for sale.