Discontinued Operations and Assets Held for Sale (Results of Operations Associated with Discontinued Operations) (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018		Jun. 30, 2019	Jun. 30, 2018
Discontinued Operations and Disposal Groups [Abstract]
Revenues	$ 159,961	$ 228,621		$ 355,373	$ 439,436
Lease operating expenses	58,160	55,406		120,876	103,016
Depreciation, depletion and amortization	2,345	47,249		33,698	95,240
Other costs and expenses (benefits)	57,401	21,474		70,481	19,023
Income before taxes	42,055	104,492		130,318	222,157
Income tax expense	17,637	33,788		56,054	73,781
Income from discontinued operations	$ 24,418	$ 70,704	[1]	$ 74,264	$ 148,376	[1],[2]

[1] Reclassified to conform to current presentation (see Note A).

[2] Reclassified to conform to current presentation (See Note A).