Revenue Recognition Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Disaggregation of Revenue [Line Items]
Oil and gas sales	$ 52,752	$ 42,412
Oil sales [Member]
Disaggregation of Revenue [Line Items]
Oil, natural gas and NGL sales	11,439	7,201
Natural gas sales [Member]
Disaggregation of Revenue [Line Items]
Oil, natural gas and NGL sales	35,767	31,063
NGL sales [Member]
Disaggregation of Revenue [Line Items]
Oil, natural gas and NGL sales	5,560	4,148
Other sales [Member]
Disaggregation of Revenue [Line Items]
Oil, natural gas and NGL sales	$ (14)	$ 0