SUPPLEMENTAL CONSOLIDATING FINANCIAL INFORMATION - Supplemental Consolidating Statement of Cash Flow Information (Detail) (USD $)	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Cash flows from operating activities:
Net income (loss)	$ (82,185,000)	$ (1,870,000)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity in income of subsidiaries	0	0
Depreciation, depletion, and amortization	40,538,000	29,823,000
Accretion of asset retirement obligation and receivable	9,288,000	6,338,000
Non-cash tax benefits	(224,000)	0
Amortization of intangible assets and liabilities, net	310,000	326,000
Share-based compensation	2,445,000	3,771,000
Gain on sales of assets	(5,000)	(308,000)
Amortization of deferred financing costs	1,209,000	1,856,000
Loss on sales of investment securities		(28,000)
Loss on extinguishment of debt	12,635,000	64,000
Loss (gain) on sales of investment securities	3,000	(28,000)
Derivative loss	5,930,000	0
Loss on foreign exchange	4,141,000	0
Income from equity affiliates	(799,000)	0
Distributions from equity affiliates	730,000	0
Changes in operating assets and liabilities:
Receivables, net	(11,270,000)	3,687,000
Inventories	22,770,000	(1,977,000)
Excess of black lung benefit obligation over trust assets	1,166,000	(281,000)
Deferred income tax	3,854,000	0
Accounts payable and accrued expenses	8,538,000	1,701,000
Deferred revenue	(8,424,000)	(6,214,000)
Income tax payable	528,000	(56,000)
Accrual for workers' compensation	(125,000)	(284,000)
Asset retirement obligations	(3,362,000)	(5,424,000)
Accrual for postretirement medical benefits	1,409,000	4,094,000
Pension and SERP obligations	(332,000)	1,517,000
Other assets and liabilities	1,805,000	(1,811,000)
Distributions received from subsidiaries	0	0
Net cash provided by operating activities	10,573,000	34,924,000
Cash flows from investing activities:
Additions to property, plant and equipment	(17,361,000)	(13,467,000)
Change in restricted investments and bond collateral and reclamation deposits	(30,517,000)	(8,714,000)
Cash payments related to Canadian acquisition	(322,637,000)	0
Cash acquired in related to Canadian acquisition	8,103,000	0
Net proceeds from sales of assets	213,000	577,000
Proceeds from sale of investments	246,000	6,807,000
Increase in loan and lease receivable	(1,120,000)	0
Receipts from loan and lease receivable	2,164,000	0
Receivable from customer for property and equipment purchases	0	(308,000)
Other	(82,000)	0
Net cash used in investing activities	(360,991,000)	(15,105,000)
Cash flows from financing activities:
Change in book overdrafts	1,605,000	1,777,000
Borrowings from long-term debt	454,219,000	0
Repayments of long-term debt	(97,538,000)	(16,070,000)
Borrowings on revolving lines of credit	10,000,000	6,000,000
Repayments on revolving lines of credit	(10,000,000)	(6,000,000)
Debt issuance costs and other refinancing costs	(27,053,000)	(182,000)
Dividends/distributions	(470,000)	(680,000)
Exercise of stock options	193,000	0
Transactions with Parent/affiliates	0	0
Net cash provided by (used in) financing activities	330,956,000	(15,155,000)
Effect of foreign exchange rates on cash	(1,038,000)	0
Net increase (decrease) in cash and cash equivalents	(20,500,000)	4,664,000
Cash and cash equivalents, beginning of period	61,110,000	31,610,000
Cash and cash equivalents, end of period	40,610,000	36,274,000
Parent/ Issuer
Cash flows from operating activities:
Net income (loss)	(82,185,000)	(1,870,000)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity in income of subsidiaries	16,148,000	(27,450,000)
Depreciation, depletion, and amortization	156,000	187,000
Accretion of asset retirement obligation and receivable	0	0
Non-cash tax benefits	(224,000)
Amortization of intangible assets and liabilities, net	0	0
Share-based compensation	1,934,000	1,567,000
Gain on sales of assets	0	0
Amortization of deferred financing costs	494,000	1,541,000
Loss on sales of investment securities		0
Loss on extinguishment of debt	62,000	64,000
Loss (gain) on sales of investment securities	0
Derivative loss	0
Loss on foreign exchange	5,233,000
Income from equity affiliates	0
Distributions from equity affiliates	0
Changes in operating assets and liabilities:
Receivables, net	943,000	(227,000)
Inventories	0	0
Excess of black lung benefit obligation over trust assets	1,166,000	(280,000)
Deferred income tax	0
Accounts payable and accrued expenses	17,348,000	(1,957,000)
Deferred revenue	0	0
Income tax payable	0	0
Accrual for workers' compensation	(125,000)	(284,000)
Asset retirement obligations	0	0
Accrual for postretirement medical benefits	(885,000)	(40,000)
Pension and SERP obligations	166,000	695,000
Other assets and liabilities	(7,429,000)	(49,000)
Distributions received from subsidiaries	76,800,000	36,600,000
Net cash provided by operating activities	29,602,000	8,497,000
Cash flows from investing activities:
Additions to property, plant and equipment	16,000	(575,000)
Change in restricted investments and bond collateral and reclamation deposits	(48,188,000)	(807,000)
Cash payments related to Canadian acquisition	(282,788,000)
Cash acquired in related to Canadian acquisition	0
Net proceeds from sales of assets	0	0
Proceeds from sale of investments	0	0
Increase in loan and lease receivable	0
Receipts from loan and lease receivable	0
Receivable from customer for property and equipment purchases	0	0
Other	0
Net cash used in investing activities	(330,960,000)	(1,382,000)
Cash flows from financing activities:
Change in book overdrafts	0	0
Borrowings from long-term debt	454,219,000
Repayments of long-term debt	(1,015,000)	(500,000)
Borrowings on revolving lines of credit	0	0
Repayments on revolving lines of credit	0	0
Debt issuance costs and other refinancing costs	(15,407,000)	(26,000)
Dividends/distributions	(470,000)	(680,000)
Exercise of stock options	193,000
Transactions with Parent/affiliates	(147,974,000)	(5,080,000)
Net cash provided by (used in) financing activities	289,546,000	(6,286,000)
Effect of foreign exchange rates on cash	0
Net increase (decrease) in cash and cash equivalents	(11,812,000)	829,000
Cash and cash equivalents, beginning of period	25,326,000	14,836,000
Cash and cash equivalents, end of period	13,514,000	15,665,000
Co-Issuer
Cash flows from operating activities:
Net income (loss)	(7,842,000)	3,829,000
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity in income of subsidiaries	0	0
Depreciation, depletion, and amortization	5,009,000	5,082,000
Accretion of asset retirement obligation and receivable	34,000	32,000
Non-cash tax benefits	0
Amortization of intangible assets and liabilities, net	290,000	312,000
Share-based compensation	14,000	23,000
Gain on sales of assets	0	0
Amortization of deferred financing costs	0	0
Loss on sales of investment securities		0
Loss on extinguishment of debt	0	0
Loss (gain) on sales of investment securities	0
Derivative loss	5,930,000
Loss on foreign exchange	0
Income from equity affiliates	0
Distributions from equity affiliates	0
Changes in operating assets and liabilities:
Receivables, net	(6,000)	(1,995,000)
Inventories	842,000	(1,632,000)
Excess of black lung benefit obligation over trust assets	0	0
Deferred income tax	0
Accounts payable and accrued expenses	(1,101,000)	4,101,000
Deferred revenue	(4,791,000)	(4,190,000)
Income tax payable	0	0
Accrual for workers' compensation	0	0
Asset retirement obligations	0	0
Accrual for postretirement medical benefits	0	0
Pension and SERP obligations	2,000	9,000
Other assets and liabilities	(273,000)	101,000
Distributions received from subsidiaries	0	0
Net cash provided by operating activities	(1,892,000)	5,672,000
Cash flows from investing activities:
Additions to property, plant and equipment	(255,000)	(698,000)
Change in restricted investments and bond collateral and reclamation deposits	5,998,000	(5,000)
Cash payments related to Canadian acquisition	0
Cash acquired in related to Canadian acquisition	0
Net proceeds from sales of assets	0	0
Proceeds from sale of investments	0	0
Increase in loan and lease receivable	0
Receipts from loan and lease receivable	0
Receivable from customer for property and equipment purchases	0	0
Other	0
Net cash used in investing activities	5,743,000	(703,000)
Cash flows from financing activities:
Change in book overdrafts	0	0
Borrowings from long-term debt	0
Repayments of long-term debt	0	0
Borrowings on revolving lines of credit	0	0
Repayments on revolving lines of credit	0	0
Debt issuance costs and other refinancing costs	0	0
Dividends/distributions	(8,500,000)	(9,000,000)
Exercise of stock options	0
Transactions with Parent/affiliates	1,723,000	(38,000)
Net cash provided by (used in) financing activities	(6,777,000)	(9,038,000)
Effect of foreign exchange rates on cash	0
Net increase (decrease) in cash and cash equivalents	(2,926,000)	(4,069,000)
Cash and cash equivalents, beginning of period	3,341,000	4,545,000
Cash and cash equivalents, end of period	415,000	476,000
Guarantor Subsidiaries
Cash flows from operating activities:
Net income (loss)	(9,722,000)	18,173,000
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity in income of subsidiaries	0	0
Depreciation, depletion, and amortization	35,373,000	24,554,000
Accretion of asset retirement obligation and receivable	9,254,000	6,305,000
Non-cash tax benefits	0
Amortization of intangible assets and liabilities, net	20,000	19,000
Share-based compensation	497,000	2,181,000
Gain on sales of assets	(5,000)	(308,000)
Amortization of deferred financing costs	715,000	315,000
Loss on sales of investment securities		(28,000)
Loss on extinguishment of debt	12,572,000	0
Loss (gain) on sales of investment securities	3,000
Derivative loss	0
Loss on foreign exchange	(1,092,000)
Income from equity affiliates	(799,000)
Distributions from equity affiliates	730,000
Changes in operating assets and liabilities:
Receivables, net	(18,474,000)	4,419,000
Inventories	21,929,000	(345,000)
Excess of black lung benefit obligation over trust assets	0	0
Deferred income tax	3,854,000
Accounts payable and accrued expenses	(3,164,000)	904,000
Deferred revenue	(3,633,000)	(2,025,000)
Income tax payable	528,000	(55,000)
Accrual for workers' compensation	0	0
Asset retirement obligations	(3,364,000)	(5,422,000)
Accrual for postretirement medical benefits	2,256,000	4,010,000
Pension and SERP obligations	(507,000)	826,000
Other assets and liabilities	4,113,000	(1,489,000)
Distributions received from subsidiaries	0	0
Net cash provided by operating activities	51,084,000	52,034,000
Cash flows from investing activities:
Additions to property, plant and equipment	(17,122,000)	(12,189,000)
Change in restricted investments and bond collateral and reclamation deposits	11,673,000	(7,902,000)
Cash payments related to Canadian acquisition	(39,849,000)
Cash acquired in related to Canadian acquisition	8,103,000
Net proceeds from sales of assets	213,000	577,000
Proceeds from sale of investments	246,000	6,807,000
Increase in loan and lease receivable	(1,120,000)
Receipts from loan and lease receivable	2,164,000
Receivable from customer for property and equipment purchases	0	(307,000)
Other	(82,000)
Net cash used in investing activities	(35,774,000)	(13,014,000)
Cash flows from financing activities:
Change in book overdrafts	1,605,000	1,777,000
Borrowings from long-term debt	0
Repayments of long-term debt	(96,523,000)	(15,561,000)
Borrowings on revolving lines of credit	10,000,000	6,000,000
Repayments on revolving lines of credit	(10,000,000)	(6,000,000)
Debt issuance costs and other refinancing costs	(11,646,000)	(156,000)
Dividends/distributions	(68,300,000)	(27,600,000)
Exercise of stock options	0
Transactions with Parent/affiliates	157,581,000	8,699,000
Net cash provided by (used in) financing activities	(17,283,000)	(32,841,000)
Effect of foreign exchange rates on cash	(1,038,000)
Net increase (decrease) in cash and cash equivalents	(3,011,000)	6,179,000
Cash and cash equivalents, beginning of period	27,451,000	10,237,000
Cash and cash equivalents, end of period	24,440,000	16,416,000
Non-Guarantor Subsidiaries
Cash flows from operating activities:
Net income (loss)	296,000	1,045,000
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity in income of subsidiaries	0	0
Depreciation, depletion, and amortization	0	0
Accretion of asset retirement obligation and receivable	0	1,000
Non-cash tax benefits	0
Amortization of intangible assets and liabilities, net	0	(5,000)
Share-based compensation	0	0
Gain on sales of assets	0	0
Amortization of deferred financing costs	0	0
Loss on sales of investment securities		0
Loss on extinguishment of debt	1,000	0
Loss (gain) on sales of investment securities	0
Derivative loss	0
Loss on foreign exchange	0
Income from equity affiliates	0
Distributions from equity affiliates	0
Changes in operating assets and liabilities:
Receivables, net	4,733,000	(239,000)
Inventories	(1,000)	0
Excess of black lung benefit obligation over trust assets	0	(1,000)
Deferred income tax	0
Accounts payable and accrued expenses	(4,526,000)	(1,146,000)
Deferred revenue	0	1,000
Income tax payable	0	(1,000)
Accrual for workers' compensation	0	0
Asset retirement obligations	2,000	(2,000)
Accrual for postretirement medical benefits	38,000	124,000
Pension and SERP obligations	7,000	(13,000)
Other assets and liabilities	(1,193,000)	(374,000)
Distributions received from subsidiaries	0	0
Net cash provided by operating activities	(643,000)	(610,000)
Cash flows from investing activities:
Additions to property, plant and equipment	0	(4,000)
Change in restricted investments and bond collateral and reclamation deposits	0	0
Cash payments related to Canadian acquisition	0
Cash acquired in related to Canadian acquisition	0
Net proceeds from sales of assets	0	0
Proceeds from sale of investments	0	0
Increase in loan and lease receivable	0
Receipts from loan and lease receivable	0
Receivable from customer for property and equipment purchases	0	(1,000)
Other	0
Net cash used in investing activities	0	(5,000)
Cash flows from financing activities:
Change in book overdrafts	0	0
Borrowings from long-term debt	0
Repayments of long-term debt	0	(9,000)
Borrowings on revolving lines of credit	0	0
Repayments on revolving lines of credit	0	0
Debt issuance costs and other refinancing costs	0	0
Dividends/distributions	0	0
Exercise of stock options	0
Transactions with Parent/affiliates	(2,108,000)	2,349,000
Net cash provided by (used in) financing activities	(2,108,000)	2,340,000
Effect of foreign exchange rates on cash	0
Net increase (decrease) in cash and cash equivalents	(2,751,000)	1,725,000
Cash and cash equivalents, beginning of period	4,992,000	1,992,000
Cash and cash equivalents, end of period	2,241,000	3,717,000
Consolidating Adjustments
Cash flows from operating activities:
Net income (loss)	17,268,000	(23,047,000)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity in income of subsidiaries	(16,148,000)	27,450,000
Depreciation, depletion, and amortization	0	0
Accretion of asset retirement obligation and receivable	0	0
Non-cash tax benefits	0
Amortization of intangible assets and liabilities, net	0	0
Share-based compensation	0	0
Gain on sales of assets	0	0
Amortization of deferred financing costs	0	0
Loss on sales of investment securities		0
Loss on extinguishment of debt	0	0
Loss (gain) on sales of investment securities	0
Derivative loss	0
Loss on foreign exchange	0
Income from equity affiliates	0
Distributions from equity affiliates	0
Changes in operating assets and liabilities:
Receivables, net	1,534,000	1,729,000
Inventories	0	0
Excess of black lung benefit obligation over trust assets	0	0
Deferred income tax	0
Accounts payable and accrued expenses	(19,000)	(201,000)
Deferred revenue	0	0
Income tax payable	0	0
Accrual for workers' compensation	0	0
Asset retirement obligations	0	0
Accrual for postretirement medical benefits	0	0
Pension and SERP obligations	0	0
Other assets and liabilities	6,587,000	0
Distributions received from subsidiaries	(76,800,000)	(36,600,000)
Net cash provided by operating activities	(67,578,000)	(30,669,000)
Cash flows from investing activities:
Additions to property, plant and equipment	0	(1,000)
Change in restricted investments and bond collateral and reclamation deposits	0	0
Cash payments related to Canadian acquisition	0
Cash acquired in related to Canadian acquisition	0
Net proceeds from sales of assets	0	0
Proceeds from sale of investments	0	0
Increase in loan and lease receivable	0
Receipts from loan and lease receivable	0
Receivable from customer for property and equipment purchases	0	0
Other	0
Net cash used in investing activities	0	(1,000)
Cash flows from financing activities:
Change in book overdrafts	0	0
Borrowings from long-term debt	0
Repayments of long-term debt	0	0
Borrowings on revolving lines of credit	0	0
Repayments on revolving lines of credit	0	0
Debt issuance costs and other refinancing costs	0	0
Dividends/distributions	76,800,000	36,600,000
Exercise of stock options	0
Transactions with Parent/affiliates	(9,222,000)	(5,930,000)
Net cash provided by (used in) financing activities	67,578,000	30,670,000
Effect of foreign exchange rates on cash	0
Net increase (decrease) in cash and cash equivalents	0	0
Cash and cash equivalents, beginning of period	0	0
Cash and cash equivalents, end of period	$ 0	$ 0