Revenue Recognition (Disaggregation of Revenue) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation of Revenue [Line Items]
Revenues and other income	$ 1,453,734	$ 1,115,848	$ 960,567
Revenues	1,473,625	1,129,786	975,596
Oil sales
Disaggregation of Revenue [Line Items]
Revenues and other income	1,412,358	1,079,703	924,618
Natural gas sales
Disaggregation of Revenue [Line Items]
Revenues and other income	10,231	9,963	11,133
CO2 sales and transportation fees
Disaggregation of Revenue [Line Items]
Revenues	$ 31,145	$ 26,182	$ 24,816