Commitments and Contingencies - Minimum lease commitments 2019 (Details) $ in Thousands	Mar. 31, 2019 USD ($)
Minimum lease commitments, Payments due by period:
2019 (excluding three months ended March 31, 2019)	$ 4,144
2020	5,233
2021	2,431
2022	1,334
2023	853
Thereafter	548
Total future minimum lease payments	14,543
Less: Imputed interest	(1,364)
Total operating lease liabilities	13,179
Operating lease liability, current	$ 4,797
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Accrued and Other Liabilities, Current
Operating lease liability, noncurrent	$ 8,382
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Operating lease liability, noncurrent
Total operating lease liabilities	$ 13,179