Discontinued operations - Depreciation, Amortization and Capital Expenditures (Details) - Discontinued Operations, Disposed of by Means Other than Sale, Spinoff - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 28, 2014
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Depreciation	$ 50,267	$ 100,002
Amortization	7,008	13,885
Capital expenditures	(20,933)	(79,622)
Payments for acquisitions, net of cash acquired	(28,668)	(113)
Payments for investments	(2,000)	(2,500)
Proceeds from investments	12,402	18,629
Publishing
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Depreciation	49,542	99,029
Amortization	7,008	13,885
Capital expenditures	(20,252)	(79,168)
Payments for acquisitions, net of cash acquired	(28,668)	(113)
Payments for investments	(2,000)	(2,500)
Proceeds from investments	12,402	18,629
Other
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Depreciation	725	973
Amortization	0	0
Capital expenditures	(681)	(454)
Payments for acquisitions, net of cash acquired	0	0
Payments for investments	0	0
Proceeds from investments	$ 0	$ 0