Fair Value Measurements - Narratives (Details) - USD ($) $ in Thousands	Mar. 30, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt and Capital Lease Obligations	$ 22,117
Assets, Fair Value Disclosure, Nonrecurring	0
Liabilities, Fair Value Disclosure, Nonrecurring	0
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible Debt, Fair Value Disclosures	127,000	$ 129,900
Debt and Capital Lease Obligations	22,100	21,800
TVN [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Postemployment Benefits Liability	$ 4,300	$ 5,100