Leases - Maturities of lease liabilities (Details) $ in Thousands	Mar. 30, 2019 USD ($)
Finance Leases
2019 (excluding the three months ended March 30, 2019)	$ 932
2020	1,028
2021	608
2022	412
2023	412
Thereafter	3,388
Total lease payments	6,780
Less imputed interest	471
Present value, Total	6,309
Operating Leases
2019 (excluding the three months ended March 30, 2019)	81,796
2020	100,986
2021	72,184
2022	46,168
2023	23,123
Thereafter	30,289
Total lease payments	354,546
Less imputed interest	27,309
Present value, Total	327,237
Total
2019 (excluding the three months ended March 30, 2019)	82,728
2020	102,014
2021	72,792
2022	46,580
2023	23,535
Thereafter	33,677
Total lease payments	$ 361,326