CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands		Mar. 31, 2016	Dec. 31, 2015
Current assets
Cash and equivalents		$ 423,063	$ 283,183
Canadian government securities with maturities greater than 90 days at the date of acquisition		146,087	173,288
Accounts receivable, less allowance for doubtful accounts of $1,605 in 2016 and 2015		521,434	522,672
Inventories, at lower of cost or market
Crude oil		31,971	25,583
Materials and supplies		134,775	141,205
Prepaid expenses		132,190	212,962
Deferred income taxes		45,498	51,183
Assets held for sale		263,912	38,340
Total current assets		1,698,930	1,448,416
Property, plant and equipment, at cost less accumulated depreciation, depletion and amortization of $12,438,436 in 2016 and $11,924,193 in 2015		9,492,348	9,818,365
Deferred charges and other assets		269,419	227,031
Total assets		11,460,697	11,493,812
Current liabilities
Current maturities of long-term debt		19,078	18,881
Accounts payable and accrued liabilities		1,338,177	1,643,632
Income taxes payable		13,552	4,819
Liabilities associated with assets held for sale		6,948	7,297
Total current liabilities		1,377,755	1,674,629
Long-term debt, including capital lease obligation		3,409,518	3,040,594
Deferred income taxes		205,913	239,811
Asset retirement obligations		823,070	793,474
Deferred credits and other liabilities		$ 439,353	$ 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		906,733	910,074
Retained earnings		5,953,132	6,212,201
Accumulated other comprehensive loss	[1]	(552,875)	(704,542)
Treasury stock, 22,860,555 shares of Common Stock in 2016 and 23,021,013 shares of Common Stock in 2015, at cost		(1,296,958)	(1,306,061)
Total stockholders' equity		5,205,088	5,306,728
Total liabilities and stockholders' equity		$ 11,460,697	$ 11,493,812

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