Condensed Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	3 Months Ended		9 Months Ended			12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017		Dec. 31, 2017		Dec. 31, 2016
Operating Activities
Net Income (Loss)	$ 54,076	$ (18,687)	$ 279,697	$ (134,683)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Stock-based compensation	6,000	5,000	16,104	27,432
Pension credit and contributions			(75,790)	(16,535)
Depreciation			40,557	41,761
Amortization of contract intangible assets and liabilities			661	649
Amortization of other intangible assets			125,043	125,001
Income on equity investments, net	(32,381)	(21,058)	(124,086)	(98,856)
Distributions from equity investments			158,926	177,953
Non-cash loss on extinguishments and modification of debt			0	8,258
Original issue discount payments			0	(7,360)
Write-downs of investment	0	0	0	180,800
Amortization of debt issuance costs and original issue discount			5,612	5,990
Gain on sales of spectrum (Note 8)	0	0	(133,197)	0
Gain on sale of business			0	(34,510)
Loss (gain) on investment transactions, net			1,113	(10,617)
Gain on sale of real estate, net		(65)	0	(365)
Other non-operating gain, net			(53)	(45)
Changes in working capital items:
Accounts receivable, net			25,264	39,192
Prepaid expenses and other current assets			(246)	13,219
Accounts payable			(2,960)	(12,001)
Employee compensation and benefits, accrued expenses and other current liabilities			(19,481)	(43,415)
Deferred revenue			2,055	(1,801)
Income taxes			(66,713)	44,710
Change in broadcast rights, net of liabilities			15,090	61,642
Deferred income taxes			68,441	(219,236)
Other, net			(9,188)	24,311
Net cash provided by operating activities			306,849	171,494
Investing Activities
Capital expenditures	(22,505)	(13,324)	(47,452)	(41,423)
Spectrum repack reimbursements			6,967	0
Net proceeds from the sale of business			0	554,487
Proceeds from FCC spectrum auction			0	172,102		$ 172,000
Proceeds from sales of real estate and other assets			66	61,240
Proceeds from the sales of investments			15,232	148,321
Distribution from equity investment			0	4,608
Other, net			1,529	780
Net cash (used in) provided by investing activities			(23,658)	900,115
Financing Activities
Long-term borrowings			0	202,694
Repayments of long-term debt			0	(703,527)
Long-term debt issuance costs			0	(1,689)
Payments of dividends			(65,776)	(564,499)
Tax withholdings related to net share settlements of share-based awards			(5,765)	(8,030)
Proceeds from stock option exercises			982	11,231
Contributions from noncontrolling interests, net			475	1,318
Net cash used in financing activities			(70,084)	(1,062,502)
Net Increase in Cash, Cash Equivalents and Restricted Cash			213,107	9,107
Cash, cash equivalents and restricted cash, beginning of period (1)			691,251	611,198	[1]	611,198	[1]
Cash, cash equivalents and restricted cash, end of period	904,358	620,305	904,358	620,305		691,251
Cash, Cash Equivalents and Restricted Cash are Comprised of:
Cash and cash equivalents	887,751	602,739	887,751	602,739		673,685
Restricted cash	16,607	17,566	16,607	17,566		17,566		$ 17,566
Cash, cash equivalents and restricted cash, end of period	$ 904,358	$ 620,305	904,358	620,305		$ 691,251
Supplemental Schedule of Cash Flow Information
Interest			135,810	130,694
Income taxes, net			$ 66,642	$ 105,678

[1] (1)Cash, cash equivalents and restricted cash at the beginning of the nine months ended September 30, 2017 of $611 million are comprised of $595 million of cash, cash equivalents and restricted cash from continuing operations as reflected in the Company’s unaudited Condensed Consolidated Balance Sheets and $16 million of cash, cash equivalents and restricted cash reflected in total assets of discontinued operations.