Acquisitions and Dispositions - Dispositions (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
	Jun. 21, 2017	Jul. 01, 2017	Jul. 02, 2016	Jul. 01, 2017	Jul. 02, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net income (loss)		$ (217)	$ (1,990)	$ (2,704)	$ 3,854
Gain (loss) on sale of business				1,631	0
Mueller-Xingrong [Member] | Disposed of by sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from divestiture of interest in joint venture	$ 18,300
Assets disposed of	56,700
Liabilities disposed of	36,200
Cumulative translation gain as a result of sale	$ 3,800
Mueller-Xingrong [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net sales				67,300	69,600
Net income (loss)				$ (9)	$ 426