Leases (Tables)

12 Months Ended

Dec. 31, 2018

Leases [Abstract]

Future minimum lease payments

The future minimum lease payments relating to operating leases are summarized as follows (in thousands of dollars):

2019	40,664
2020	27,064
2021	17,663
2022	11,521
2023	6,677
2024 and after	8,923
	112,512