Condensed Consolidating Financial Statements (Cash Flows) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jul. 01, 2014
Operating activities
Net cash flows provided by operating activities	$ 49,049	$ 41,283
Investing activities
Capital expenditures	(26,466)	(35,105)
Return of investment in NPCQB	0	0
Proceeds from sale-leaseback transactions	1,408
Proceeds from sale or disposition of assets	548	2,373
Net cash used in investing activities	(24,510)	(32,732)
Financing activities
Payment of accrued purchase price to sellers	0	(10,875)
Net payments on debt	(3,119)	(8,665)
Issuance of debt	0	40,000
Distribution to parent	0	0
Other		(753)
Net cash (used in) provided by financing activities	(3,119)	19,707
Net change in cash and cash equivalents	21,420	28,258
Beginning cash and cash equivalents	12,063	20,035
Ending cash and cash equivalents	33,483	48,293
Parent Guarantor: Holdings
Operating activities
Net cash flows provided by operating activities	0	0
Investing activities
Capital expenditures	0	0
Return of investment in NPCQB	0	0
Proceeds from sale-leaseback transactions	0
Proceeds from sale or disposition of assets	0	0
Net cash used in investing activities	0	0
Financing activities
Payment of accrued purchase price to sellers		0
Net payments on debt	0	0
Issuance of debt		0
Distribution to parent	0	0
Other		0
Net cash (used in) provided by financing activities	0	0
Net change in cash and cash equivalents	0	0
Beginning cash and cash equivalents	0	0
Ending cash and cash equivalents	0	0
Subsidiary Issuer: NPC
Operating activities
Net cash flows provided by operating activities	37,079	31,824
Investing activities
Capital expenditures	(20,214)	(32,895)
Return of investment in NPCQB	5,713	7,622
Proceeds from sale-leaseback transactions	1,408
Proceeds from sale or disposition of assets	499	2,351
Net cash used in investing activities	(12,594)	(22,922)
Financing activities
Payment of accrued purchase price to sellers		(10,875)
Net payments on debt	(3,119)	(8,665)
Issuance of debt		40,000
Distribution to parent	0	0
Other		(753)
Net cash (used in) provided by financing activities	(3,119)	19,707
Net change in cash and cash equivalents	21,366	28,609
Beginning cash and cash equivalents	11,278	19,170
Ending cash and cash equivalents	32,644	47,779
Subsidiary Co-Issuer: NPCQB
Operating activities
Net cash flows provided by operating activities	11,970	9,459
Investing activities
Capital expenditures	(6,252)	(2,210)
Return of investment in NPCQB	0	0
Proceeds from sale-leaseback transactions	0
Proceeds from sale or disposition of assets	49	22
Net cash used in investing activities	(6,203)	(2,188)
Financing activities
Payment of accrued purchase price to sellers		0
Net payments on debt	0
Distribution to parent	(5,713)	(7,622)
Other		0
Net cash (used in) provided by financing activities	(5,713)	(7,622)
Net change in cash and cash equivalents	54	(351)
Beginning cash and cash equivalents	785	865
Ending cash and cash equivalents	839	514
Subsidiary Co-Issuer: NPC Op Co B
Operating activities
Net cash flows provided by operating activities	0	0
Investing activities
Capital expenditures	0	0
Return of investment in NPCQB	0	0
Proceeds from sale-leaseback transactions	0
Proceeds from sale or disposition of assets	0	0
Net cash used in investing activities	0	0
Financing activities
Payment of accrued purchase price to sellers		0
Net payments on debt	0	0
Issuance of debt		0
Distribution to parent	0	0
Other		0
Net cash (used in) provided by financing activities	0	0
Net change in cash and cash equivalents	0	0
Beginning cash and cash equivalents	0	0
Ending cash and cash equivalents	0	0
Eliminations
Operating activities
Net cash flows provided by operating activities	0	0
Investing activities
Capital expenditures	0	0
Return of investment in NPCQB	(5,713)	(7,622)
Proceeds from sale-leaseback transactions	0
Proceeds from sale or disposition of assets	0	0
Net cash used in investing activities	(5,713)	(7,622)
Financing activities
Payment of accrued purchase price to sellers		0
Net payments on debt	0
Issuance of debt		0
Distribution to parent	5,713	7,622
Other		0
Net cash (used in) provided by financing activities	5,713	7,622
Net change in cash and cash equivalents	0	0
Beginning cash and cash equivalents	0	0
Ending cash and cash equivalents	$ 0	$ 0