Earnings per Unit (Details) - $ / shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 24, 2017	Sep. 25, 2016	Sep. 24, 2017	Sep. 25, 2016
Earnings Per Unit [Abstract]
Basic weighted average units outstanding (in shares)	56,078	55,948	56,062	55,922
Effect of dilutive units:
Deferred units (in shares)	44	33	41	30
Performance units (in shares)	0	0	48	43
Restricted units (in shares)	284	253	292	266
Unit options (in shares)	185	131	188	131
Diluted weighted average units outstanding (in shares)	56,591	56,365	56,631	56,392
Net income (loss) per limited partner unit - basic (in dollars per share)	$ 3.41	$ 3.13	$ 2.82	$ 3.30
Net income (loss) per limited partner unit - diluted (in dollars per share)	$ 3.38	$ 3.10	$ 2.79	$ 3.27