Other Data - State Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
State income tax expense
Texas gross margins tax	$ 550	$ 586	$ 608
Total state income tax expense	550	586	608
State income tax payments, net of refunds and collections	$ 543	$ 637	$ 555