Fair Value of Financial Instruments, Significant Unobservable Inputs Roll Forward (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 01, 2018	Jul. 02, 2017	Jul. 01, 2018	Jul. 02, 2017	Dec. 31, 2017
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of year			$ (23,980)	$ (28,770)
Gain from change in fair value			434	270
Balance at end of period	$ (23,546)	$ (28,500)	(23,546)	(28,500)
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other income, net	(2,969)	6,010	5,623	17,396
Fair Value, Measurements, Recurring [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Alternative Investments, Fair Value Disclosure	24,219	23,967	24,219	23,967	$ 24,436
Other income, net	$ (342)	$ 384	$ 106	$ 1,015