Leases - Maturities of our operating leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Maturities of operating leases
2020	$ 3,245
2021	2,784
2022	2,422
2023	1,909
2024	1,183
Later years	5,004
Less imputed interest	(2,612)
Operating lease liabilities	13,935
Operating lease rent expense		$ 4,900	$ 3,800
Undiscounted future minimum obligations related to this lease	$ 2,000	7,400
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2019		3,817
2020		3,081
2021		2,671
2022		2,244
2023		1,941
Later years		8,870
Minimum lease commitments		$ 22,624