Supplemental Consolidated Financial Statement Information - Disaggregated Revenues (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) segment	Dec. 31, 2019 USD ($)
Number of business segments | segment	1
Operating Revenues	$ 86,100	$ 145,773
United States
Operating Revenues	73,983	129,452
Canada
Operating Revenues	$ 12,117	$ 16,321