Consolidated Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Statement [Abstract]
Revenues	$ 3,014,357	$ 3,768,126	$ 3,883,039
Costs, expenses and other operating
Cost of sales (exclusive of items shown separately below)	2,663,136	3,155,099	2,980,354
Depreciation, depletion and amortization	426,442	492,211	420,980
Amortization of acquired sales contracts, net	(9,457)	(25,189)	(22,069)
Sales contract amortization	(9,457)	(25,189)	(22,069)
Change in fair value of coal derivatives and coal trading activities, net	7,845	(16,590)	(2,907)
Coal derivative settlements, non-hedging	(32,534)	(43,990)	7
Asset impairment and mine closure costs	220,879	539,182	7,316
Goodwill, Impairment Loss	265,423	330,680	0
Contract settlement resulting from Patriot Coal bankruptcy	0	58,335	0
Reduction in accrual related to acquired litigation		79,532	0
Acquisition and transition costs	0	0	47,360
Selling, general and administrative expenses	133,448	134,299	119,056
Other operating expense (income), net	2,316	(19,367)	(10,119)
Total operating expenses	3,677,498	4,525,138	3,539,978
Income from investment in subsidiaries
Income (loss) from operations	(663,141)	(757,012)	343,061
Interest expense, net
Interest expense	(381,267)	(317,615)	(230,186)
Interest and investment income	6,603	5,473	3,309
Interest Income (Expense), Nonoperating, Net	(374,664)	(312,142)	(226,877)
Nonoperating expense
Net loss resulting from early retirement and refinancing of debt	(42,921)	(23,668)	(1,958)
Debt Related Commitment Fees and Debt Issuance Costs	0	0	(49,490)
Nonoperating expense, net	(42,921)	(23,668)	(51,448)
Loss from continuing operations before income taxes	(1,080,726)	(1,092,822)	64,736
Benefit from income taxes	(335,498)	(353,907)	(24,279)
Income (loss) from continuing operations	(745,228)	(738,915)	89,015
Income from discontinued operations, including gain on sale - net of tax	103,396	55,228	53,825
Net income (loss)	(641,832)	(683,687)	142,840
Less: Net income attributable to noncontrolling interest		(268)	(1,157)
Net income (loss) attributable to Arch Coal, Inc.	(641,832)	(683,955)	141,683
Earnings (loss) per common share
Income (Loss) from Continuing Operations, Per Basic Share	$ (3.52)	$ (3.50)	$ 0.47
Income (Loss) from Continuing Operations, Per Diluted Share	$ (3.52)	$ (3.50)	$ 0.47
Basic earnings (loss) per common share	$ (3.03)	$ (3.24)	$ 0.75
Diluted earnings (loss) per common share	$ (3.03)	$ (3.24)	$ 0.74
Weighted average shares outstanding
Basic, weighted average shares outstanding	212,098	211,381	190,086
Diluted, weighted average shares outstanding	212,098	211,381	190,905
Dividends declared per common share	$ 0.12	$ 0.20	$ 0.43
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	$ (587,633)	$ (692,239)	$ 141,240