Leases - Narrative (Details) $ in Thousands		1 Months Ended
	Mar. 06, 2019 a item	Jan. 31, 2017 USD ($) a	Jun. 30, 2019 USD ($) ft²	Mar. 31, 2019 USD ($)	Jan. 01, 2019 USD ($)
Leases
Operating lease right-of-use assets, net			$ 1,608
Operating lease liability			$ 2,057
Accounting Standards Update 2016-02
Leases
Cumulative effect adjustment from adoption of ASU 2016-01				$ 213
Accounting Standards Update 2016-02 | Proforma Adjustment
Leases
Operating lease right-of-use assets, net		$ 2,300
Operating lease liability		$ 2,300
Accounting Standards Update 2016-02 | Adjustments
Leases
Operating lease right-of-use assets, net					$ 1,600
Operating lease liability					1,900
Deferred rent					(100)
Cumulative effect adjustment from adoption of ASU 2016-01					$ 200
Office space lease
Leases
Area of property leased | ft²			38,300
Operating lease right-of-use assets, net			$ 976
Land leases
Leases
Operating lease right-of-use assets, net			$ 632
City Of Texas City and State Of Texas (Galveston Bay) | Surface leases
Leases
Area of land leased/to be leased | a		994
Term of lease agreement		36 months
Existence of option to extend		true
Option to extend term		12 months
BND | Land leases
Leases
Area of land leased/to be leased | a	984
Term of lease agreement	30 years
Maximum period for automatic extension for Outside Effective Date	6 months
Number of renewal term | item	2
Option to extend term	10 years
Option to extend term, lease not yet commenced	true