Condensed Consolidating Financial Statements (Statements of Operations) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jul. 01, 2014	Jun. 30, 2015	Jul. 01, 2014
Condensed Consolidating Statements of Income
Total sales	$ 306,236	$ 285,906	$ 615,444	$ 582,159
Total costs and expenses	296,885	279,603	589,906	561,459
Operating income	9,351	6,303	25,538	20,700
Interest expense	10,492	10,042	20,957	20,204
Equity in net income of subsidiary	0	0	0	0
(Loss) income before income taxes	(1,141)	(3,739)	4,581	496
Income tax benefit	(1,213)	(2,365)	(466)	(1,086)
Net income	72	(1,374)	5,047	1,582
Parent Guarantor: Holdings
Condensed Consolidating Statements of Income
Total sales	0	0	0	0
Total costs and expenses	0	0	0	0
Operating income	0	0	0	0
Interest expense	0	0	0	0
Equity in net income of subsidiary	72	(1,374)	5,047	1,582
(Loss) income before income taxes	72	(1,374)	5,047	1,582
Income tax benefit	0	0	0	0
Net income	72	(1,374)	5,047	1,582
Subsidiary Issuer: NPC
Condensed Consolidating Statements of Income
Total sales	253,911	252,847	514,478	519,215
Total costs and expenses	247,557	247,780	493,409	499,750
Operating income	6,354	5,067	21,069	19,465
Interest expense	10,492	10,042	20,957	20,204
Equity in net income of subsidiary	3,643	797	4,923	788
(Loss) income before income taxes	(495)	(4,178)	5,035	49
Income tax benefit	(567)	(2,804)	(12)	(1,533)
Net income	72	(1,374)	5,047	1,582
Subsidiary Co-Issuer: NPCQB
Condensed Consolidating Statements of Income
Total sales	52,325	33,059	100,966	62,944
Total costs and expenses	49,328	31,823	96,497	61,709
Operating income	2,997	1,236	4,469	1,235
Interest expense	0	0	0	0
Equity in net income of subsidiary	0	0	0	0
(Loss) income before income taxes	2,997	1,236	4,469	1,235
Income tax benefit	(646)	439	(454)	447
Net income	3,643	797	4,923	788
Subsidiary Co-Issuer: NPC Op Co B
Condensed Consolidating Statements of Income
Total sales	0	0	0	0
Total costs and expenses	0	0	0	0
Operating income	0	0	0	0
Interest expense	0	0	0	0
Equity in net income of subsidiary	0	0	0	0
(Loss) income before income taxes	0	0	0	0
Income tax benefit	0	0	0	0
Net income	0	0	0	0
Eliminations
Condensed Consolidating Statements of Income
Total sales	0	0	0	0
Total costs and expenses	0	0	0	0
Operating income	0	0	0	0
Interest expense	0	0	0	0
Equity in net income of subsidiary	(3,715)	577	(9,970)	(2,370)
(Loss) income before income taxes	(3,715)	577	(9,970)	(2,370)
Income tax benefit	0	0	0	0
Net income	$ (3,715)	$ 577	$ (9,970)	$ (2,370)