Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Tax credits	$ 0	$ 0
Tax loss carryforwards	44,285	62,436
Other	3,612	2,829
Deferred tax assets, gross	47,897	65,265
Valuation allowance	(47,897)	(65,265)
Deferred income tax assets, net	0	0
Deferred tax liabilities:
Property basis difference	(6,996)	(7,174)
Net deferred tax liabilities	$ (6,996)	$ (7,174)