Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 572,344	$ 1,103,540
Trading securities	0	286,396
Accounts receivable (less accumulated provision for doubtful accounts: $5,961 at June 30, 2017 and $6,923 at December 31, 2016)	310,975	341,628
Derivative instruments, at fair value	85,442	33,053
Prepaid expenses and other	28,092	63,602
Total current assets	996,853	1,828,219
Property, plant and equipment	19,769,299	18,216,775
Less: accumulated depreciation and depletion	5,512,037	5,054,559
Net property, plant and equipment	14,257,262	13,162,216
Restricted cash	0	75,000
Investment in nonconsolidated entity	260,737	184,562
Other assets	209,159	222,925
Total assets	15,724,011	15,472,922
Current liabilities:
Current portion of long-term debt	707,189	0
Accounts payable	368,422	309,978
Derivative instruments, at fair value	107,880	257,943
Other current liabilities	172,235	236,719
Total current liabilities	1,355,726	804,640
Long-term debt	2,584,973	3,289,459
Deferred income taxes	1,876,324	1,760,004
Other liabilities and credits	529,418	499,572
Total liabilities	6,346,441	6,353,675
Shareholders’ equity:
Common stock, no par value, authorized 320,000 shares, shares issued: 177,896 at June 30, 2017 and 177,896 at December 31, 2016	3,440,691	3,440,185
Treasury stock, shares at cost: 4,569 at June 30, 2017 (including 250 held in rabbi trust) and 5,069 at December 31, 2016 (including 226 held in rabbi trust)	(82,000)	(91,019)
Retained earnings	2,703,778	2,509,073
Accumulated other comprehensive (loss) income	(293)	2,042
Total common shareholders’ equity	6,062,176	5,860,281
Noncontrolling interests in consolidated subsidiaries	3,315,394	3,258,966
Total equity	9,377,570	9,119,247
Total liabilities and equity	$ 15,724,011	$ 15,472,922

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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Namespace Prefix:	us-gaap_
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.