Fair Value Measurements Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 30, 2019		Dec. 29, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		$ 0		$ 2,000
Available-for-sale Securities, Amortized Cost Basis	[1]	27,615		30,035
conversion of debt		(2,000)
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure				3,730
Available-for-sale Securities		0	[1]	0
Convertible Debt, Fair Value Disclosures				0
Derivative Asset		0		0
Assets, Fair Value Disclosure		0		3,730
Derivative Liability		0		0
Financial and Nonfinancial Liabilities, Fair Value Disclosure		0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	[2]			0
Available-for-sale Securities	[2]	27,363	[1]	29,605
Convertible Debt, Fair Value Disclosures	[2]			0
Derivative Asset	[2]	6,311		776
Assets, Fair Value Disclosure	[2]	33,674		30,381
Derivative Liability	[2]	235		1,130
Financial and Nonfinancial Liabilities, Fair Value Disclosure	[2]	235		1,130
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	[3]			0
Available-for-sale Securities	[3]	0	[1]	0
Convertible Debt, Fair Value Disclosures	[3]			2,000
Derivative Asset	[3]	0		0
Assets, Fair Value Disclosure	[3]	0		2,000
Derivative Liability		0		0	[3]
Financial and Nonfinancial Liabilities, Fair Value Disclosure		$ 0		$ 0	[3]

[1] As of March 30, 2019, the Company’s investments had maturity dates ranging from May 2019 to March 2021.

[2] Level 2 fair value estimates are based on observable inputs other than quoted prices in active markets for identical assets and liabilities, quoted prices for identical or similar assets or liabilities in inactive markets, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.

[3] Level 3 fair value estimates are based on inputs that are generally unobservable and typically reflect management’s estimates of assumptions that market participants would use in pricing the asset or liability. The fair values are therefore determined using model-based techniques, including option pricing and discounted cash flow models. Unobservable inputs used in the models are significant to the fair values of the assets and liabilities.