Consolidated Statements of Income and Comprehensive Income - USD ($) shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net Operating Revenues and Other
Crude Oil and Condensate		$ 6,256,396	$ 4,317,341	$ 4,934,562
Natural Gas Liquids		729,561	437,250	407,658
Natural Gas		921,934	742,152	1,061,038
Gains (Losses) on Mark-to-Market Commodity Derivative Contracts		19,828	(99,608)	61,924
Gathering, Processing and Marketing		3,298,087	1,966,259	2,253,135
Gains (Losses) on Asset Dispositions, Net		(99,096)	205,835	(8,798)
Other, Net	[1]	81,610	81,403	47,909
Total		11,208,320	7,650,632	8,757,428
Operating Expenses
Lease and Well		1,044,847	927,452	1,182,282
Transportation Costs	[1]	740,352	764,106	849,319
Gathering and Processing Costs		148,775	122,901	146,156
Exploration Costs		145,342	124,953	149,494
Dry Hole Costs	[1]	4,609	10,657	14,746
Impairments		479,240	620,267	6,613,546
Marketing Costs		3,330,237	2,007,635	2,385,982
Depreciation, Depletion and Amortization		3,409,387	3,553,417	3,313,644
General and Administrative		434,467	394,815	366,594
Taxes Other Than Income		544,662	349,710	421,744
Total		10,281,918	8,875,913	15,443,507
Operating Income (Loss)		926,402	(1,225,281)	(6,686,079)
Other Income (Expense), Net		9,152	(50,543)	1,916
Income (Loss) Before Interest Expense and Income Taxes		935,554	(1,275,824)	(6,684,163)
Interest Expense
Incurred		301,801	313,341	279,234
Capitalized		(27,429)	(31,660)	(41,841)
Net Interest Expense		274,372	281,681	237,393
Income (Loss) Before Income Taxes		661,182	(1,557,505)	(6,921,556)
Income Tax Benefit		(1,921,397)	(460,819)	(2,397,041)
Net Income (Loss)		$ 2,582,579	$ (1,096,686)	$ (4,524,515)
Net Income (Loss) Per Share
Basic		$ 4.49	$ (1.98)	$ (8.29)
Diluted		4.46	(1.98)	(8.29)
Dividends Declared per Common Share		$ 0.670	$ 0.670	$ 0.670
Average Number of Common Shares [Abstract]
Basic (in shares)		574,620	553,384	545,697
Diluted		578,693	553,384	545,697
Other Comprehensive Income (Loss)
Foreign Currency Translation Adjustments		$ 2,799	$ 12,097	$ (11,517)
Other, Net of Tax		(3,086)	2,231	1,235
Other Comprehensive Income (Loss)		(287)	14,328	(10,282)
Comprehensive Income (Loss)		$ 2,582,292	$ (1,082,358)	$ (4,534,797)

[1] Excludes gains or losses on the mark-to-market of financial commodity derivative contracts, gains or losses on sales of reserves and related assets, interest charges and general corporate expenses for each of the three years in the period ended December 31, 2017.