Condensed Consolidating Financial Statements (Statements of Income) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Apr. 01, 2014
Condensed Consolidating Statements of Income
Total sales	$ 309,208	$ 296,253
Total costs and expenses	293,021	281,856
Operating income	16,187	14,397
Interest expense	10,465	10,162
Equity in net income of subsidiary	0	0
Income before income taxes	5,722	4,235
Income tax expense	747	1,279
Net income	4,975	2,956
Parent Guarantor: Holdings
Condensed Consolidating Statements of Income
Total sales	0	0
Total costs and expenses	0	0
Operating income	0	0
Interest expense	0	0
Equity in net income of subsidiary	4,975	2,965
Income before income taxes	4,975	2,965
Income tax expense	0	0
Net income	4,975	2,965
Subsidiary Issuer: NPC
Condensed Consolidating Statements of Income
Total sales	260,567	266,368
Total costs and expenses	245,852	251,970
Operating income	14,715	14,398
Interest expense	10,465	10,162
Equity in net income of subsidiary	1,280	(9)
Income before income taxes	5,530	4,227
Income tax expense	555	1,271
Net income	4,975	2,956
Subsidiary Co-Issuer: NPCQB
Condensed Consolidating Statements of Income
Total sales	48,641	29,885
Total costs and expenses	47,169	29,886
Operating income	1,472	(1)
Interest expense	0	0
Equity in net income of subsidiary	0	0
Income before income taxes	1,472	(1)
Income tax expense	192	8
Net income	1,280	(9)
Subsidiary Co-Issuer: NPC Op Co B
Condensed Consolidating Statements of Income
Total sales	0	0
Total costs and expenses	0	0
Operating income	0	0
Interest expense	0	0
Equity in net income of subsidiary	0	0
Income before income taxes	0	0
Income tax expense	0	0
Net income	0	0
Eliminations
Condensed Consolidating Statements of Income
Total sales	0	0
Total costs and expenses	0	0
Operating income	0	0
Interest expense	0	0
Equity in net income of subsidiary	(6,255)	(2,956)
Income before income taxes	(6,255)	(2,956)
Income tax expense	0	0
Net income	$ (6,255)	$ (2,956)