Leases - Real estate leases other information (Details) $ in Thousands	3 Months Ended
	Mar. 26, 2019 USD ($) lease
Leases
Cash paid for amounts included in measurement of operating lease liabilities	$ 11,948
Right-of-use assets obtained in exchange for new operating lease liabilities	$ 8,340
Weighted-average remaining lease term	17 years 9 months 22 days
Weighted-average discount rate	6.78%
Operating lease not yet taken possession	$ 27,900
Number of finance leases | lease	1
Right-of-use asset	$ 1,800
Lease liability	$ 2,100