Fair Value of Financial Instruments, Significant Unobservable Inputs Roll Forward (Details) - USD ($) $ in Thousands	3 Months Ended
	Apr. 01, 2018	Apr. 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	315	60
Balance at end of period	(23,665)	(28,710)
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other income, net	8,592	11,386
Fair Value, Measurements, Recurring [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Alternative Investments, Fair Value Disclosure	24,584	23,603	$ 24,436
Other income, net	$ 448	$ 631