Supplemental Guarantor and Non-Guarantor Financial Information (Details 5) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Supplemental guarantor and non-guarantor financial information
Cash flows provided by (used in) operating activities	$ (27,076,000)	$ 329,907,000	$ 706,866,000
INVESTING ACTIVITIES
Additions to property, plant and equipment	(153,896,000)	(391,512,000)	(436,705,000)
Proceeds from sales of investments	1,559,000	13,239,000	27,325,000
Other	1,824,000	898,000	1,413,000
Cash flows used in investing activities	(150,513,000)	(377,375,000)	(2,840,660,000)
FINANCING ACTIVITIES
Proceeds from issuance of debt	897,412,000	496,510,000	2,350,000,000
Borrowings under revolving credit agreement	764,332,000	510,650,000	71,259,000
Repayments on revolving credit agreement	(764,332,000)	(519,453,000)	(61,259,000)
Retirements of debt	(515,195,000)	(392,851,000)	(290,630,000)
Dividends paid	(16,889,000)	(31,246,000)	(30,042,000)
Tax effect from stock-based compensation arrangements	(717,000)	217,000	8,929,000
Proceeds from stock-options exercised	279,000	161,000	8,920,000
Cash paid upon exercise of warrants		(11,535,000)
Debt issuance costs	(41,588,000)	(24,532,000)	(80,027,000)
Other	(293,000)	(766,000)	(5,203,000)
Cash flows provided by financing activities	323,009,000	27,155,000	1,971,947,000
Cash flows provided by (used in) continuing operations	145,420,000	(20,313,000)	(161,847,000)
CASH FLOWS FROM DISCONTINUED OPERATIONS
Cash flows provided by investing activities		9,500,000
Cash flows provided by (used in) discontinued operations		9,500,000
Effect of foreign exchange rates on cash	(1,203,000)	(1,016,000)	(3,668,000)
Net increase (decrease) in cash and cash equivalents	144,217,000	(11,829,000)	(165,515,000)
Cash and cash equivalents at beginning of year	116,601,000	128,430,000	293,410,000
Add: Cash and cash equivalents of discontinued operations at beginning of year			535,000
Cash and cash equivalents at end of year	260,818,000	116,601,000	128,430,000
Western Coal Corp
INVESTING ACTIVITIES
Acquisition, net of cash acquired			(2,432,693,000)
FINANCING ACTIVITIES
Cash paid upon exercise of warrants		(11,500,000)
Parent (Issuer)
Supplemental guarantor and non-guarantor financial information
Cash flows provided by (used in) operating activities	(204,982,000)	(373,256,000)	(569,306,000)
INVESTING ACTIVITIES
Additions to property, plant and equipment	(2,294,000)	(4,395,000)	(93,000)
Intercompany loans made	(40,236,000)	(293,170,000)	(50,738,000)
Intercompany payments received	30,500,000	16,513,000
Investments in equity affiliates		(238,083,000)
Distributions from equity affiliates		271,847,000	516,407,000
Other			23,000
Cash flows used in investing activities	(12,030,000)	(247,288,000)	(2,001,159,000)
FINANCING ACTIVITIES
Proceeds from issuance of debt	897,412,000	496,510,000	2,350,000,000
Retirements of debt	(496,062,000)	(343,255,000)	(258,062,000)
Dividends paid	(16,889,000)	(31,246,000)	(30,042,000)
Tax effect from stock-based compensation arrangements	(717,000)	217,000	8,929,000
Proceeds from stock-options exercised	279,000	161,000	8,920,000
Cash paid upon exercise of warrants		(11,535,000)
Debt issuance costs	(41,588,000)	(24,532,000)	(80,027,000)
Advances from (to) consolidated entities	25,072,000	519,737,000	380,623,000
Other	(178,000)	(766,000)	(5,203,000)
Cash flows provided by financing activities	367,329,000	605,291,000	2,375,138,000
Cash flows provided by (used in) continuing operations		(15,253,000)
CASH FLOWS FROM DISCONTINUED OPERATIONS
Net increase (decrease) in cash and cash equivalents	150,317,000	(15,253,000)	(195,327,000)
Cash and cash equivalents at beginning of year	83,833,000	99,086,000	294,413,000
Cash and cash equivalents at end of year	234,150,000	83,833,000	99,086,000
Parent (Issuer) | Western Coal Corp
INVESTING ACTIVITIES
Acquisition, net of cash acquired			(2,466,758,000)
Guarantor Subsidiaries
Supplemental guarantor and non-guarantor financial information
Cash flows provided by (used in) operating activities	236,491,000	734,325,000	1,047,651,000
INVESTING ACTIVITIES
Additions to property, plant and equipment	(127,873,000)	(143,206,000)	(143,529,000)
Other		855,000	273,000
Cash flows used in investing activities	(127,873,000)	(142,351,000)	(143,256,000)
FINANCING ACTIVITIES
Retirements of debt	(19,133,000)	(8,131,000)	(12,300,000)
Advances from (to) consolidated entities	(89,330,000)	(570,342,000)	(374,321,000)
Investment from Parent		238,083,000
Intercompany dividends		(261,102,000)	(516,407,000)
Other	(115,000)
Cash flows provided by financing activities	(108,578,000)	(601,492,000)	(903,028,000)
Cash flows provided by (used in) continuing operations		(9,518,000)
CASH FLOWS FROM DISCONTINUED OPERATIONS
Cash flows provided by investing activities		9,500,000
Cash flows provided by (used in) discontinued operations		9,500,000
Net increase (decrease) in cash and cash equivalents	40,000	(18,000)	1,367,000
Cash and cash equivalents at beginning of year	61,000	79,000	(1,823,000)
Add: Cash and cash equivalents of discontinued operations at beginning of year				535,000
Cash and cash equivalents at end of year	101,000	61,000	79,000
Non-Guarantor Subsidiaries
Supplemental guarantor and non-guarantor financial information
Cash flows provided by (used in) operating activities	(58,585,000)	(31,162,000)	228,521,000
INVESTING ACTIVITIES
Additions to property, plant and equipment	(23,729,000)	(243,911,000)	(293,083,000)
Proceeds from sales of investments	1,559,000	13,239,000	27,325,000
Other	1,824,000	43,000	1,117,000
Cash flows used in investing activities	(20,346,000)	(230,629,000)	(230,576,000)
FINANCING ACTIVITIES
Borrowings under revolving credit agreement	764,332,000	510,650,000	71,259,000
Repayments on revolving credit agreement	(764,332,000)	(519,453,000)	(61,259,000)
Retirements of debt		(41,465,000)	(20,268,000)
Advances from (to) consolidated entities	64,258,000	50,605,000	(6,302,000)
Intercompany borrowings	40,236,000	293,170,000	50,738,000
Intercompany payments made	(30,500,000)	(16,513,000)
Intercompany dividends		(10,745,000)
Cash flows provided by financing activities	73,994,000	266,249,000	34,168,000
Cash flows provided by (used in) continuing operations		4,458,000
CASH FLOWS FROM DISCONTINUED OPERATIONS
Effect of foreign exchange rates on cash	(1,203,000)	(1,016,000)	(3,668,000)
Net increase (decrease) in cash and cash equivalents	(6,140,000)	3,442,000	28,445,000
Cash and cash equivalents at beginning of year	32,707,000	29,265,000	820,000
Cash and cash equivalents at end of year	26,567,000	32,707,000	29,265,000
Non-Guarantor Subsidiaries | Western Coal Corp
INVESTING ACTIVITIES
Acquisition, net of cash acquired			34,065,000
Eliminations
INVESTING ACTIVITIES
Intercompany loans made	40,236,000	293,170,000	50,738,000
Intercompany payments received	(30,500,000)	(16,513,000)
Investments in equity affiliates		238,083,000
Distributions from equity affiliates		(271,847,000)	(516,407,000)
Cash flows used in investing activities	9,736,000	242,893,000	(465,669,000)
FINANCING ACTIVITIES
Intercompany borrowings	(40,236,000)	(293,170,000)	(50,738,000)
Intercompany payments made	30,500,000	16,513,000
Investment from Parent		(238,083,000)
Intercompany dividends		271,847,000	516,407,000
Cash flows provided by financing activities	$ (9,736,000)	$ (242,893,000)	$ 465,669,000