Leases (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Lessee, Lease, Description [Line Items]
Operating	$ 5,628	$ 5,628	$ 0
Current Operating	2,077	2,077
Noncurrent Operating	3,598	3,598	0
Total operating lease liability	5,675	5,675
Lease, Cost
Operating lease costs	620	1,778
Short-term lease costs	169	722
Sublease income	(99)	(147)
Net lease costs	$ 690	2,353
Cash paid for amounts included in the measurement of lease liabilities, Operating cash flows from operating leases		1,757
Right-of-use assets obtained in exchange for lease obligations, Operating leases		$ 576
Weighted average discount rate, Operating leases	5.88%	5.88%
Weighted average remaining lease term, Operating leases (in years)	3 years 1 month 6 days	3 years 1 month 6 days
Maturities of Operating Lease Liabilities
Remainder of 2019	$ 596	$ 596
2020	2,278	2,278
2021	1,684	1,684
2022	1,079	1,079
2023	496	496
After 2023	57	57
Total lease payments	6,190	6,190
Less interest	(515)	(515)
Total operating lease liability	5,675	5,675
Rental payments, minimum rentals and rental expenses			2,081	$ 2,372	$ 2,561
Annual commitments under non-cancellable operating leases, next five years	6,897	6,897
Annual commitments under non-cancellable operating lease, after 5 years	$ 55	$ 55
Maturity of Operating Lease Liabilities
2019			2,224
2020			1,858
2021			1,357
2022			977
2023			481
After 2023			55
Total lease commitments			$ 6,952
Minimum
Lessee, Lease, Description [Line Items]
Remaining lease terms	1 year	1 year
Maximum
Lessee, Lease, Description [Line Items]
Remaining lease terms	5 years	5 years