CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 845,641	$ 182,055
Accounts receivable (less accumulated provision for doubtful accounts: $5,171 in 2013; $5,883 in 2012)	235,781	190,258
Inventory	19,656	45,165
Derivative instruments, at fair value	107,647	304,237
Prepaid expenses and other	46,700	38,451
Assets of discontinued operations		92,678
Total current assets	1,255,425	852,844
Equity in nonconsolidated investments	128,983	130,368
Property, plant and equipment	11,062,136	9,153,207
Less: accumulated depreciation and depletion	2,728,374	2,093,795
Net property, plant and equipment	8,333,762	7,059,412
Other assets	73,883	57,182
Noncurrent assets of discontinued operations		750,056
Total assets	9,792,053	8,849,862
Current liabilities:
Current portion of long-term debt	11,162	23,204
Accounts payable	330,329	276,802
Derivative instruments, at fair value	29,651	75,562
Other current liabilities	152,268	146,605
Liabilities of discontinued operations		48,291
Total current liabilities	523,410	570,464
Long-term debt	2,490,354	2,502,969
Deferred income taxes	1,655,765	1,442,071
Other liabilities and credits	258,396	187,941
Noncurrent liabilities of discontinued operations		257,615
Total liabilities	4,927,925	4,961,060
Stockholders' equity
Common stock, no par value, authorized 320,000 shares, shares issued: 175,684 in 2013 and 2012	1,869,843	1,770,545
Treasury stock, shares at cost: 24,800 in 2013 and 25,575 in 2012	(447,738)	(461,774)
Retained earnings	2,567,980	2,195,502
Accumulated other comprehensive income	44,703	99,547
Total common stockholders' equity	4,034,788	3,603,820
Noncontrolling interests in consolidated subsidiaries	829,340	284,982
Total equity	4,864,128	3,888,802
Total liabilities and equity	$ 9,792,053	$ 8,849,862