Leases - Future lease payments (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Operating leases
2019 (remaining)	$ 2,011
2020	7,301
2021	5,073
2022	3,829
2023	3,042
Thereafter	9,412
Total undiscounted lease payments	30,668
Less: Imputed interest	(3,697)
Present value of lease payments	26,971
Finance leases
2019 (remaining)	2,315
2020	7,440
2021	3,430
2022	737
Total undiscounted lease payments	13,922
Less: Imputed interest	(1,222)
Present value of lease payments	$ 12,700
Operating leases under ASC 840
2019		$ 6,638
2020		4,618
2021		3,487
2022		2,195
2023		1,426
Thereafter		3,339
Total		$ 21,703