Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 25, 2016	Dec. 31, 2015	Dec. 31, 2014
Noncash or Part Noncash Acquisitions [Line Items]
Deferred Revenue, Revenue Recognized		$ 8,000	$ 5,800	$ 8,200
Restricted Cash and Investments, Current		800	1,000
Noncash or Part Noncash Acquisition, Fixed Assets Acquired		4,000	1,100	6,400
Foreign Currency Transaction Gain (Loss), before Tax	$ 400		1,200	1,000
Research and Development Expense	3,800		2,600	$ 4,400
Deferred Tax Liabilities, Net, Noncurrent	$ 3,628	$ 3,628	$ 8,094