Leases - Future lease payments (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Operating leases
2019 (remaining)	$ 5,880
2020	6,801
2021	4,352
2022	3,221
2023	2,257
Thereafter	6,566
Total undiscounted lease payments	29,077
Less: Imputed interest	3,551
Present value of lease payments	25,526
Finance leases
2019 (remaining)	6,320
2020	6,684
2021	2,553
2022	76
2023
Thereafter
Total undiscounted lease payments	15,633
Less: Imputed interest	1,452
Present value of lease payments	$ 14,181
Operating leases before Topic 842
2019		$ 6,638
2020		4,618
2021		3,487
2022		2,195
2023		1,426
Thereafter		3,339
Total		$ 21,703