CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Current assets
Cash and equivalents	$ 997,207	$ 872,797
Canadian government securities with maturities greater than 90 days at the date of acquisition		111,542
Accounts receivable, less allowance for doubtful accounts of $1,605 in 2017 and 2016	267,209	357,099
Inventories, at lower of cost or market	120,066	127,071
Prepaid expenses	39,427	63,604
Assets held for sale	23,248	27,070
Total current assets	1,447,157	1,559,183
Property, plant and equipment, at cost less accumulated depreciation, depletion and amortization of $12,027,902 in 2017 and $12,607,815 in 2016	8,283,738	8,316,188
Deferred income taxes	406,703	365,935
Deferred charges and other assets	55,161	54,554
Total assets	10,192,759	10,295,860
Current liabilities
Current maturities of long-term debt	9,781	569,817
Accounts payable	584,025	784,975
Income taxes payable	57,687	13,920
Other taxes payable	30,160	28,167
Other accrued liabilities	146,607	102,777
Liabilities associated with assets held for sale	3,270	2,776
Total current liabilities	831,530	1,502,432
Long-term debt, including capital lease obligation	2,908,285	2,422,750
Deferred income taxes	108,756	69,081
Asset retirement obligations	747,602	681,528
Deferred credits and other liabilities	616,452	617,490
Liabilities associated with assets held for sale		85,900
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 2017 and 2016	195,056	195,056
Capital in excess of par value	910,936	916,799
Retained earnings	5,575,175	5,729,596
Accumulated other comprehensive loss	(425,504)	(628,212)
Treasury stock	(1,275,529)	(1,296,560)
Total stockholders' equity	4,980,134	4,916,679
Total liabilities and stockholders' equity	$ 10,192,759	$ 10,295,860

Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount due from customers or clients, within one year of the balance sheet date (or the normal operating cycle, whichever is longer), for goods or services (including trade receivables) that have been delivered or sold in the normal course of business, reduced to the estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.