CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Operating Activities
Net income (loss)		$ (275,970)		$ (2,270,833)		$ 905,611
Adjustments to reconcile net income (loss) to net cash provided by continuing operations activities:
Loss from discontinued operations		2,027		15,061		119,362
Depreciation, depletion and amortization		1,054,081		1,619,824		1,906,247
Impairment of assets		95,088		2,493,156		51,314
Amortization of deferred major repair costs		3,794		7,296		8,345
Dry hole costs		15,047		296,845		269,986
Amortization of undeveloped leases		43,417		75,312		74,438
Accretion of asset retirement obligations		46,742		48,665		50,778
Deferred income tax benefits		(387,843)		(978,030)		(170,915)
Pretax gains from disposition of assets		(1,663)		(154,155)		(138,903)
Net (increase) decrease in noncash operating working capital		(38,689)		35,064		(3,729)
Other operating activities, net		44,764		(4,836)		(23,895)
Net cash provided by continuing operations activities		600,795		1,183,369		3,048,639
Investing Activities
Property additions and dry hole costs		(926,948)		(2,549,736)		(3,679,464)
Proceeds from sales of property, plant and equipment		1,155,144		423,911		1,467,046
Purchase of investment securities	[1]	(695,879)		(911,787)		(986,328)
Proceeds from maturity of investment securities	[1]	761,000		1,129,139		899,857
Other investing activities, net		(7,230)		(13,648)		(18,929)
Net cash provided (required) by investing activities		286,087		(1,922,121)		(2,317,818)
Financing Activities
Borrowings of debt		541,444		600,000		100,000
Repayments of debt		(600,000)		(450,000)
Capital lease obligation payments		(10,447)		(10,434)		(25,265)
Purchase of treasury stock				(250,000)		(375,000)
Issue cost of debt facility		(14,085)
Cash dividends paid		(206,635)		(244,998)		(236,371)
Other financing activities, net		(1,158)		(9,129)		(8,074)
Net cash required by financing activities		(290,881)		(364,561)		(544,710)
Cash Flows from Discontinued Operations
Operating activities				(15,005)		(39,563)
Investing activities				5,314		199,541
Changes in cash included in current assets held for sale				192,585		100,790
Net increase in cash and cash equivalents of discontinued operations				182,894		260,768
Effect of exchange rate changes on cash and cash equivalents		(6,387)		10,294		(3,726)
Net increase (decrease) in cash and cash equivalents		589,614		(910,125)		443,153
Cash and cash equivalents at January 1		283,183	[2]	1,193,308		750,155
Cash and cash equivalents at December 31		$ 872,797		$ 283,183	[2]	$ 1,193,308

[1] Investments are Canadian government securities with maturities greater than 90 days at the date of acquisition.

[2] Reclassified to conform to current presentation. See Note B for additional information.