Condensed Consolidating Financial Statements (Statements of Income) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 28, 2016	Jun. 30, 2015	Jun. 28, 2016	Jun. 30, 2015
Condensed Consolidating Statements of Income
Total sales	$ 303,985	$ 306,236	$ 623,519	$ 615,444
Total costs and expenses	291,235	296,885	593,002	589,906
Operating income	12,750	9,351	30,517	25,538
Interest expense	11,205	10,492	22,542	20,957
Equity in net income of subsidiary	0	0	0	0
Income (loss) before income taxes	1,545	(1,141)	7,975	4,581
Income tax expense (benefit)	274	(1,213)	(955)	(466)
Net income	1,271	72	8,930	5,047
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	(5,638)	(3,715)	(16,262)	(9,970)
Income (loss) before income taxes	(5,638)	(3,715)	(16,262)	(9,970)
Income tax expense (benefit)	0	0	0	0
Net income	(5,638)	(3,715)	(16,262)	(9,970)
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	1,271	72	8,930	5,047
Income (loss) before income taxes	1,271	72	8,930	5,047
Income tax expense (benefit)	0	0	0	0
Net income	1,271	72	8,930	5,047
Subsidiary Issuer: NPC
Condensed Consolidating Statements of Income
Total sales	250,388	253,911	518,982	514,478
Total costs and expenses	241,750	247,557	495,107	493,409
Operating income	8,638	6,354	23,875	21,069
Interest expense	11,205	10,492	22,542	20,957
Equity in net income of subsidiary	4,367	3,643	7,332	4,923
Income (loss) before income taxes	1,800	(495)	8,665	5,035
Income tax expense (benefit)	529	(567)	(265)	(12)
Net income	1,271	72	8,930	5,047
Subsidiary Co-Issuer: NPCQB
Condensed Consolidating Statements of Income
Total sales	53,597	52,325	104,537	100,966
Total costs and expenses	49,485	49,328	97,895	96,497
Operating income	4,112	2,997	6,642	4,469
Interest expense	0	0	0	0
Equity in net income of subsidiary	0	0	0	0
Income (loss) before income taxes	4,112	2,997	6,642	4,469
Income tax expense (benefit)	(255)	(646)	(690)	(454)
Net income	4,367	3,643	7,332	4,923
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
Income (loss) before income taxes	0	0	0	0
Income tax expense (benefit)	0	0	0	0
Net income	$ 0	$ 0	$ 0	$ 0