Earnings per Unit (Details) - $ / shares shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 28, 2015	Jun. 29, 2014	Jun. 28, 2015	Jun. 29, 2014
Basic weighted average units outstanding	55,734	55,419	55,696	55,453
Effect of dilutive units:
Incremental units attributable to dilutive effect of deferred units	21	5	0	0
Incremental units attributable to dilutive effect of restricted untis	366	184	0	0
Incremental Units Attributable To Share Based Payment Arrangements	135	136	0	0
Incremental Units Attributable To Phantom Unit Options	29	80	0	0
Diluted weighted average units outstanding	56,285	55,824	55,696	55,453
Net income (loss) per limited partner unit - basic	$ 1.03	$ 0.79	$ (0.47)	$ (0.71)
Net income (loss) per limited partner unit - diluted	$ 1.02	$ 0.79	$ (0.47)	$ (0.71)