Fair Value Measurements - Narratives (Details) - USD ($) $ in Thousands	Sep. 29, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt and Capital Lease Obligations	$ 22,873	$ 21,190
Defined Benefit Plan, Benefit Obligation	5,100	4,300
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	114,200	143,500
Debt and Capital Lease Obligations	22,900
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities measured and recorded at fair value	6,049	9,690
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities measured and recorded at fair value	45	40
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities measured and recorded at fair value	$ 6,004	$ 9,650