CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands		Jun. 30, 2016	Dec. 31, 2015
Current assets
Cash and equivalents		$ 267,483	$ 283,183
Canadian government securities with maturities greater than 90 days at the date of acquisition		131,224	173,288
Accounts receivable, less allowance for doubtful accounts of $1,605 in 2016 and 2015		293,312	522,672
Inventories, at lower of cost or market
Crude oil		8,654	25,583
Materials and supplies		145,413	141,205
Prepaid expenses		113,563	212,962
Deferred income taxes		46,093	51,183
Assets held for sale		32,113	38,340
Total current assets		1,037,855	1,448,416
Property, plant and equipment, at cost less accumulated depreciation, depletion and amortization of $12,241,549 in 2016 and $11,924,193 in 2015		8,565,485	9,818,365
Deferred charges and other assets		311,292	227,031
Total assets		9,914,632	11,493,812
Current liabilities
Current maturities of long-term debt		20,011	18,881
Accounts payable and accrued liabilities		843,787	1,643,632
Income taxes payable		12,816	4,819
Liabilities associated with assets held for sale		4,135	7,297
Total current liabilities		880,749	1,674,629
Long-term debt, including capital lease obligation		2,435,486	3,040,594
Deferred income taxes		46,749	239,811
Asset retirement obligations		746,361	793,474
Deferred credits and other liabilities		633,594	438,576
Stockholders' equity
Cumulative Preferred Stock, par $100, authorized 400,000 shares, none issued
Common Stock, par $1.00, authorized 450,000,000 shares, issued 195,055,724 shares in 2016 and 2015		195,056	195,056
Capital in excess of par value		914,236	910,074
Retained earnings		5,895,794	6,212,201
Accumulated other comprehensive loss	[1]	(536,659)	(704,542)
Treasury stock, 22,856,616 shares of Common Stock in 2016 and 23,021,013 shares of Common Stock in 2015, at cost		(1,296,734)	(1,306,061)
Total stockholders' equity		5,171,693	5,306,728
Total liabilities and stockholders' equity		$ 9,914,632	$ 11,493,812

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