Leases - Maturities of lease liabilities (Details) $ in Thousands	Jun. 29, 2019 USD ($)
Finance Leases
2019 (excluding the six months ended June 29, 2019)	$ 477
2020	1,034
2021	738
2022	488
2023	418
Thereafter	2,930
Total lease payments	6,085
Less imputed interest	59
Present value, Total	6,026
Operating Leases
2019 (excluding the six months ended June 29, 2019)	61,429
2020	110,389
2021	82,494
2022	55,932
2023	29,997
Thereafter	43,162
Total lease payments	383,403
Less imputed interest	33,214
Present value, Total	350,189
Total
2019 (excluding the six months ended June 29, 2019)	61,906
2020	111,423
2021	83,232
2022	56,420
2023	30,415
Thereafter	46,092
Total lease payments	$ 389,488