Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended	36 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Additional income tax benefit					$ 600
Percent of eligible investments for Oklahoma tax credit	1.00%		1.00%
Period of eligible investments for Oklahoma tax credit			5 years
Additional tax credit on certain capital expenditure, percent					1.00%
Income tax benefit	$ (560)	$ (5,527)	$ (7,924)	$ (9,398)	$ 300	$ 900
Expected effective income tax rate for the year			24.00%