Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Current assets
Cash and cash equivalents	$ 494,788	$ 734,231
Short term investments	199,731	248,954
Restricted cash	50,409	5,678
Trade accounts receivable	217,667	211,506
Other receivables	21,742	20,511
Inventories	239,035	190,253
Prepaid royalties	10,352	11,118
Deferred income taxes	20,454	52,728
Coal derivative assets	13,743	13,257
Other current assets	51,398	54,515
Total current assets	1,319,319	1,542,751
Property, plant and equipment, net	4,173,038	6,453,458
Other assets
Prepaid royalties	29,867	66,806
Equity investments	206,347	235,842
Other noncurrent assets	119,426	130,866
Total other assets	355,640	433,514
Total assets	5,847,997	8,429,723
Current liabilities
Accounts payable	152,229	180,113
Accrued expenses and other current liabilities	310,747	302,396
Current maturities of debt	32,237	36,885
Total current liabilities	495,213	519,394
Long-term debt	5,108,492	5,123,485
Asset retirement obligations	414,194	398,896
Accrued pension benefits	12,061	16,260
Accrued postretirement benefits other than pension	33,966	32,668
Accrued workers’ compensation	95,905	94,291
Deferred income taxes	44,806	422,809
Other noncurrent liabilities	248,800	153,766
Total liabilities	6,453,437	6,761,569
Stockholders' deficit
Common stock, $0.01 par value, authorized 26,000 shares, issued 21,443 shares and 21,379 shares at September 30, 2015 and December 31, 2014, respectively	2,145	2,141
Paid-in capital	3,052,910	3,048,460
Treasury stock, at cost, 152 shares at September 30, 2015 and December 31, 2014	(53,863)	(53,863)
Accumulated deficit	(3,612,599)	(1,331,825)
Accumulated other comprehensive income	5,967	3,241
Total stockholders’ deficit	(605,440)	1,668,154
Total liabilities and stockholders’ deficit	$ 5,847,997	$ 8,429,723