Earnings per Unit (Details) - $ / shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2019	Sep. 23, 2018	Sep. 29, 2019	Sep. 23, 2018
Earnings Per Unit [Abstract]
Basic weighted average units outstanding (in shares)	56,519	56,231	56,344	56,205
Effect of dilutive units:
Deferred units (in shares)	48	46	51	46
Performance units (in shares)	0	0	33	49
Restricted units (in shares)	239	277	263	289
Unit options (in shares)	125	142	125	164
Diluted weighted average units outstanding (in shares)	56,931	56,696	56,816	56,753
Net income (loss) per unit - basic (in dollars per share)	$ 3.36	$ 3.79	$ 3.01	$ 2.65
Net income (loss) per unit - diluted (in dollars per share)	$ 3.34	$ 3.76	$ 2.98	$ 2.63