Fair Value Measurements - Narratives (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 28, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Debts, Excluding Capital Leases	$ 20,461
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible Debt, Fair Value Disclosures	148,600	$ 129,900
Other Debts, Excluding Capital Leases	20,500	21,800
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities measured and recorded at fair value	0
Total assets measured and recorded at fair value	0
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, Fair Value Remeasurement	0
Total liabilities measured and recorded at fair value	195	4
Total assets measured and recorded at fair value	5	55
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	195	4
Total assets measured and recorded at fair value	5	33
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	0	0
Total assets measured and recorded at fair value	0	0
TVN [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Postemployment Benefits Liability	$ 3,200	$ 5,100