Business Acquisitions Business Acquisitions - Narrative (Details) - USD ($)			3 Months Ended		6 Months Ended
	Oct. 13, 2016	Oct. 12, 2016	Jul. 02, 2017	Jul. 03, 2016	Jul. 02, 2017	Jul. 03, 2016	Dec. 31, 2016
Business Acquisition [Line Items]
Net income			$ 8,970,000	$ 3,813,000	$ 13,742,000	$ 7,685,000
Goodwill, Purchase Accounting Adjustments					1.5
Net revenues			151,231,000	146,392,000	296,439,000	297,190,000
Operating Income (Loss)			11,404,000	5,347,000	18,758,000	10,842,000
Downstream [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross		$ 195,000,000
Business acquisition, net of cash acquired	$ 198,000,000
Business Combination, Contingent Consideration, Liability		15,000,000
Purchase price		216,034,000
Fair value of accounts receivables acquired		28,100,000
Contingent Consideration Classified as Equity, Fair Value Disclosure			0		0		$ 12,200,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Instruments Classified in Shareholders' Equity, Period Increase (Decrease)			9,700,000		12,200,000
Net revenues			20,300,000		42,700,000
Operating Income (Loss)			$ 13,300,000		$ 14,800,000
Schroedahl [Member]
Business Acquisition [Line Items]
Acquisition-related costs				$ 100,000		$ 200,000
Earn-Out Minimum Target [Member] | Downstream [Member]
Business Acquisition [Line Items]
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High		15,000,000
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, Low		7,500,000
Business Combination, Contingent Consideration, Liability		$ 0