Leases - Maturities of lease liabilities (Details) $ in Thousands	Sep. 28, 2019 USD ($)
Finance Leases
2019 (excluding the nine months ended September 28, 2019)	$ 432
2020	1,647
2021	1,258
2022	1,022
2023	926
Thereafter	8,987
Total lease payments	14,272
Less imputed interest	1,602
Present value, Total	12,670
Operating Leases
2019 (excluding the nine months ended September 28, 2019)	31,316
2020	116,032
2021	88,122
2022	59,951
2023	32,688
Thereafter	42,182
Total lease payments	370,291
Less imputed interest	29,049
Present value, Total	341,242
Total
2019 (excluding the nine months ended September 28, 2019)	31,748
2020	117,679
2021	89,380
2022	60,973
2023	33,614
Thereafter	51,169
Total lease payments	$ 384,563