Acquisition (Details) - USD ($)	9 Months Ended
	Sep. 25, 2016	Dec. 27, 2015	Sep. 27, 2015
Business Acquisition [Line Items]
Goodwill	$ 604,700,000	$ 592,695,000	$ 592,781,000
Boulder Media [Member]
Business Acquisition [Line Items]
Date of Acquisition	Jul. 13, 2016
Business Acquisition, Name of Acquired Entity	Boulder Media Limited
Payments to Acquire Businesses, Gross	$ 13,200,000
Goodwill	$ 11,800,000