Acquisitions and dispositions (Details Textual) (USD $)	3 Months Ended			9 Months Ended				9 Months Ended			9 Months Ended
	Jun. 29, 2014	Jun. 29, 2014 Investment Classified Ventures [Member]	Sep. 28, 2014 Investment Classified Ventures [Member]	Sep. 28, 2014 London Broadcasting Company [Member]	Sep. 29, 2013 London Broadcasting Company [Member]	Jul. 08, 2014 London Broadcasting Company [Member] station	Oct. 01, 2014 Classified Ventures [Member] Subsequent Event [Member]	Sep. 28, 2014 Unsecured Fixed Rate Notes 4.875 Percent Due September 2021 [Member]	Sep. 08, 2014 Unsecured Fixed Rate Notes 4.875 Percent Due September 2021 [Member]	Dec. 29, 2013 Unsecured Fixed Rate Notes 4.875 Percent Due September 2021 [Member]	Sep. 28, 2014 Unsecured Fixed Rate Notes 5.500 Percent Due September 2024 [Member]	Sep. 08, 2014 Unsecured Fixed Rate Notes 5.500 Percent Due September 2024 [Member]	Dec. 29, 2013 Unsecured Fixed Rate Notes 5.500 Percent Due September 2024 [Member]
Acquisitions Investments and Disposals [Line Items]
Equity Method Investment, Ownership Percentage			26.90%
Proceeds from Divestiture of Businesses and Interests in Affiliates		$ 585,000,000
Proceeds from Equity Method Investment, Dividends or Distributions		154,600,000
Proceeds From Sale Of Assets	407,500,000
Number Of Television Stations						6
Significant Acquisitions and Disposals, Acquisition Costs or Sale Proceeds						215,000,000	1,800,000,000
Escrow deposit disbursement related to London Broadcasting Company television stations acquisition				(134,908,000)	0
Business Acquisition, Percentage of Voting Interests Acquired							73.00%
Debt Instrument, Face Amount								$ 350,000,000	$ 350,000,000	$ 0	$ 325,000,000	$ 325,000,000	$ 0
Debt Instrument, Interest Rate, Stated Percentage								4.875%	4.875%		5.50%	5.50%
Debt Instrument, Maturity Date								Sep. 15, 2021			Sep. 15, 2024