Discontinued operations - Balance Sheet Disclosures (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 28, 2014	Dec. 29, 2013	Dec. 30, 2012
Current assets
Cash and cash equivalents	$ 0	$ 8,179	$ 14,180	$ 65,542
Total current assets	6,608	490,531
Intangible and other assets
Total noncurrent assets	657	1,920,415
Current liabilities
Total current liabilities	5,243	424,739
Total noncurrent liabilities	$ 0	1,025,413
Discontinued Operations, Disposed of by Means Other than Sale, Spinoff
Current assets
Cash and cash equivalents		8,179
Trade receivables, net of allowances		378,418
Other receivables		17,722
Inventories		38,861
Prepaid expenses and other current assets		28,917
Assets held for sale		18,434
Total current assets		490,531
Property and equipment
Cost		2,608,677
Less accumulated depreciation		(1,666,202)
Net property and equipment		942,475
Intangible and other assets
Goodwill		591,445
Indefinite-lived and amortizable intangible assets less accumulated amortization		62,015
Deferred income taxes		261,321
Investments and other assets		63,159
Total intangible and other assets		977,940
Total noncurrent assets		1,920,415
Total assets		2,410,946
Current liabilities
Accounts payable		132,884
Compensation		81,799
Taxes		26,874
Other		92,856
Deferred income		90,326
Total current liabilities		424,739
Postretirement medical and life insurance liabilities		93,474
Pension liabilities		770,040
Other noncurrent liabilities		161,899
Total noncurrent liabilities		1,025,413
Total liabilities		1,450,152
Publishing | Discontinued Operations, Disposed of by Means Other than Sale, Spinoff
Current assets
Cash and cash equivalents		8,024
Trade receivables, net of allowances		357,523
Other receivables		16,422
Inventories		38,861
Prepaid expenses and other current assets		27,883
Assets held for sale		18,434
Total current assets		467,147
Property and equipment
Cost		2,590,159
Less accumulated depreciation		(1,655,676)
Net property and equipment		934,483
Intangible and other assets
Goodwill		544,345
Indefinite-lived and amortizable intangible assets less accumulated amortization		50,115
Deferred income taxes		261,321
Investments and other assets		63,125
Total intangible and other assets		918,906
Total noncurrent assets		1,853,389
Total assets		2,320,536
Current liabilities
Accounts payable		125,888
Compensation		77,606
Taxes		26,195
Other		89,096
Deferred income		77,123
Total current liabilities		395,908
Postretirement medical and life insurance liabilities		93,474
Pension liabilities		770,040
Other noncurrent liabilities		161,899
Total noncurrent liabilities		1,025,413
Total liabilities		1,421,321
Other | Discontinued Operations, Disposed of by Means Other than Sale, Spinoff
Current assets
Cash and cash equivalents		155
Trade receivables, net of allowances		20,895
Other receivables		1,300
Inventories		0
Prepaid expenses and other current assets		1,034
Assets held for sale		0
Total current assets		23,384
Property and equipment
Cost		18,518
Less accumulated depreciation		(10,526)
Net property and equipment		7,992
Intangible and other assets
Goodwill		47,100
Indefinite-lived and amortizable intangible assets less accumulated amortization		11,900
Deferred income taxes		0
Investments and other assets		34
Total intangible and other assets		59,034
Total noncurrent assets		67,026
Total assets		90,410
Current liabilities
Accounts payable		6,996
Compensation		4,193
Taxes		679
Other		3,760
Deferred income		13,203
Total current liabilities		28,831
Postretirement medical and life insurance liabilities		0
Pension liabilities		0
Other noncurrent liabilities		0
Total noncurrent liabilities		0
Total liabilities		$ 28,831