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Financial Instruments (Details) - USD ($)	3 Months Ended		6 Months Ended
Financial Instruments (Details) - USD ($)	Jul. 01, 2017	Jul. 02, 2016	Jul. 01, 2017	Jul. 02, 2016	Dec. 31, 2016
Derivative [Line Items]
Interest rate cap hedges recognized in other comprehensive income, net of tax	$ 122,000	$ 148,000	$ 243,000	$ 556,000
Other Current Assets
Derivative [Line Items]
Derivative asset	0		0		$ 0
Other Long Term Assets
Derivative [Line Items]
Derivative asset	167,000		167,000		553,000
Interest rate cap premiums
Derivative [Line Items]
Interest rate cap hedges recognized in other comprehensive income, net of tax	100,000
Gain (loss) on derivatives, net	0
Cash Flow Hedging \| Designated as Hedging Instrument \| Interest rate cap premiums \| Other Current Assets
Derivative [Line Items]
Derivative asset	0		0		0
Cash Flow Hedging \| Designated as Hedging Instrument \| Interest rate cap premiums \| Other Long Term Assets
Derivative [Line Items]
Derivative asset	$ 167,000		$ 167,000		$ 553,000