Leases - Supplemental cash flow information (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 27, 2020	Jun. 29, 2019
Cash paid for amounts included in measurement of lease liabilities:
Operating cash flows from operating leases	$ 61,535	$ 63,910
Operating cash flows from finance leases	230	26
Financing cash flows from finance leases	2,819	732
Right-of-use assets obtained in exchange for lease obligations:
Operating leases	50,270	90,091
Finance leases	3,675	195
Amortization of right of use operating lease assets	$ 60,324	$ 56,950