Operating Leases - Balance Sheet Presentation (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Balance Sheet Captions
Right-of-use assets	$ 1,003
Operating lease liabilities, current	368	$ 0
Operating lease liabilities	1,078
Other Assets [Member]
Balance Sheet Captions
Right-of-use assets	1,003
Accrued Liabilities [Member]
Balance Sheet Captions
Operating lease liabilities, current	368
Other Long-Term Liabilities [Member]
Balance Sheet Captions
Operating lease liabilities, noncurrent	$ 710