CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands		Dec. 31, 2015	Dec. 31, 2014
Current assets
Cash and cash equivalents		$ 283,183	$ 1,193,308	[1]
Canadian government securities with maturities greater than 90 days at the date of acquisition		173,288	461,313	[1]
Accounts receivable, less allowance for doubtful accounts of $1,605 in 2015 and $1,609 in 2014		522,672	873,277	[1]
Inventories, at lower of cost or market		166,788	242,733	[1]
Prepaid expenses		212,962	77,281	[1]
Deferred income taxes		51,183	55,107	[1]
Assets held for sale		38,340	376,130	[1]
Total current assets		1,448,416	3,279,149	[1]
Property, plant and equipment, at cost less accumulated depreciation, depletion and amortization of $11,294,193 in 2015 and $9,503,524 in 2014		9,818,365	13,331,047	[1]
Deferred charges and other assets		227,031	62,582	[1]
Assets held for sale	[1]		50,960
Total assets		11,493,812	16,723,738	[1]
Current liabilities
Current maturities of long-term debt		18,881	465,388	[1],[2]
Accounts payable		1,529,848	2,275,830	[1]
Income taxes payable		4,819	59,054	[1]
Other taxes payable		38,498	52,457	[1]
Other accrued liabilities		75,286	143,610	[1]
Liabilities associated with assets held for sale		7,297	151,548	[1]
Total current liabilities		1,674,629	3,147,887	[1]
Long-term debt, including capital lease obligation		3,040,594	2,517,669	[1],[2]
Deferred income taxes		239,811	1,193,864	[1]
Asset retirement obligations		793,474	841,526	[1]
Deferred credits and other liabilities		$ 438,576	441,048	[1]
Liabilities associated with assets held for sale	[1]		$ 8,310
Stockholders' equity
Cumulative Preferred Stock, par $100, authorized 400,000 shares, none issued				[1]
Common Stock, par $1.00, authorized 450,000,000 shares, issued 195,055,724 shares in 2015 and 195,040,149 shares in 2014		$ 195,056	$ 195,040	[1]
Capital in excess of par value		910,074	906,741	[1]
Retained earnings		6,212,201	8,728,032	[1]
Accumulated other comprehensive loss	[3]	(704,542)	(170,255)	[1]
Treasury stock		(1,306,061)	(1,086,124)	[1]
Total stockholders' equity		5,306,728	8,573,434	[1]
Total liabilities and stockholders' equity		$ 11,493,812	$ 16,723,738	[1]

[1] Reclassified to conform to current presentation.

[2] Reclassified to current presentation

[3] All amounts are presented net of income taxes.