Business Acquisitions (Narrative) (Details)				3 Months Ended								6 Months Ended	12 Months Ended
	Oct. 13, 2016 USD ($)	Oct. 12, 2016 USD ($) employee	Apr. 15, 2015 USD ($)	Dec. 31, 2016 USD ($)	Oct. 02, 2016 USD ($)	Jul. 03, 2016 USD ($)	Apr. 03, 2016 USD ($)	Dec. 31, 2015 USD ($)	Oct. 04, 2015 USD ($)	Jul. 05, 2015 USD ($)	Apr. 05, 2015 USD ($)	Jul. 03, 2016 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Payments to Acquire Businesses, Net of Cash Acquired													$ 197,489,000	$ 79,983,000	$ 0
Net revenues				$ 158,236,000	$ 134,833,000	$ 146,392,000	$ 150,798,000	$ 164,243,000	$ 159,258,000	$ 166,906,000	$ 165,860,000		590,259,000	656,267,000	841,446,000
Operating income (loss)													10,918,000	26,174,000	64,757,000
Long-term Line of Credit				251,200,000				90,500,000					251,200,000	90,500,000
Goodwill, acquired during period													93,425,000	49,387,000
Revenues													994,000	1,124,000	1,783,000
Net income				(2,002,000)	$ 4,418,000	$ 3,813,000	$ 3,872,000	$ 7,156,000	$ (8,078,000)	$ 1,872,000	$ 8,912,000		10,101,000	9,863,000	$ 50,386,000
Downstream [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash consideration		$ 195,000,000
Contingent consideration		15,000,000
Payments to Acquire Businesses, Net of Cash Acquired	$ 198,000,000
Contingent Consideration Classified as Equity, Fair Value Disclosure				$ 12,200,000									12,200,000
Acquisition related costs		1,000,000
Acquired receivables, fair value		$ 28,100,000
Net revenues													18,900,000
Operating income (loss)													500,000
Schroedahl [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Payments to Acquire Businesses, Net of Cash Acquired			$ 79,900,000
Acquisition related costs												$ 1,000,000	200,000	900,000
Acquired receivables, fair value			4,300,000
Goodwill, acquired during period												$ 13,200,000
Revenues													25,700,000	21,000,000
Net income													$ 1,700,000	$ 1,200,000
Line of Credit [Member] | Schroedahl [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Long-term Line of Credit			$ 23,800,000
Critical Flow Solutions [Member] | Downstream [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Entity number of employees | employee		200
Earn-Out Minimum Target [Member] | Downstream [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Contingent consideration		$ 0
Range of outcome for contingent consideration, minimum		7,500,000
Range of outcome for contingent consideration, maximum		$ 15,000,000