SUPPLEMENTAL CONSOLIDATING FINANCIAL INFORMATION - Supplemental Consolidating Statement of Cash Flow Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Cash flows from operating activities:
Net loss	$ (19,030)	$ (4,087)
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	16,059	14,426
Accretion of asset retirement obligation and receivable	3,479	3,180
Non-cash tax benefits	(138)	0
Amortization of intangible assets and liabilities, net	153	164
Share-based compensation	728	2,386
Loss (gain) on sales of assets	38	(234)
Amortization of deferred financing costs	271	933
Loss on sales of investment securities	0	7
Loss on foreign exchange	6,790	0
Changes in operating assets and liabilities:
Receivables, net	5,202	120
Inventories	4,525	(2,687)
Excess of black lung benefit obligation over trust assets	701	83
Accounts payable and accrued expenses	10,959	3,245
Deferred revenue	(1,302)	160
Income tax payable	28	27
Accrual for workers' compensation	(69)	(191)
Asset retirement obligations	(1,352)	(3,207)
Accrual for postretirement medical benefits	906	1,985
Pension and SERP obligations	(293)	742
Other assets and liabilities	1,993	4,164
Distributions received from subsidiaries	0	0
Net cash provided by operating activities	29,648	21,216
Cash flows from investing activities:
Additions to property, plant and equipment	(3,050)	(5,301)
Change in restricted investments and bond collateral and reclamation deposits	(465,544)	(6,435)
Net proceeds from sales of assets	0	441
Proceeds from sale of restricted investments	0	5,619
Receivable from customer for property and equipment purchases	(10)	(49)
Other	(60)	0
Net cash used in investing activities	(468,664)	(5,725)
Cash flows from financing activities:
Change in book overdrafts	(315)	820
Borrowings from long-term debt	454,219	0
Repayments of long-term debt	(6,239)	(6,573)
Borrowings on revolving lines of credit	0	6,000
Repayments on revolving lines of credit	0	(6,000)
Debt issuance costs and other refinancing costs	(7,598)	(156)
Dividends/distributions	(261)	(340)
Transactions with Parent/affiliates	0	0
Net cash provided by (used in) financing activities	439,806	(6,249)
Net increase (decrease) in cash and cash equivalents	790	9,242
Cash and cash equivalents, beginning of period	61,110	31,610
Cash and cash equivalents, end of period	61,900	40,852
Parent/ Issuer
Cash flows from operating activities:
Net loss	(19,030)	(4,087)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity in income of subsidiaries	(13,319)	(10,304)
Depreciation, depletion, and amortization	76	94
Accretion of asset retirement obligation and receivable	0	0
Non-cash tax benefits	(138)
Amortization of intangible assets and liabilities, net	0	0
Share-based compensation	569	682
Loss (gain) on sales of assets	0	0
Amortization of deferred financing costs	149	771
Loss on sales of investment securities		0
Loss on foreign exchange	6,790
Changes in operating assets and liabilities:
Receivables, net	(178)	49
Inventories	0	0
Excess of black lung benefit obligation over trust assets	701	83
Accounts payable and accrued expenses	5,670	(8,202)
Deferred revenue	0	0
Income tax payable	0	0
Accrual for workers' compensation	(69)	(191)
Asset retirement obligations	0	0
Accrual for postretirement medical benefits	(374)	(100)
Pension and SERP obligations	83	320
Other assets and liabilities	(183)	(187)
Distributions received from subsidiaries	42,500	19,600
Net cash provided by operating activities	23,247	(1,472)
Cash flows from investing activities:
Additions to property, plant and equipment	38	(157)
Change in restricted investments and bond collateral and reclamation deposits	(471,151)	(398)
Net proceeds from sales of assets		0
Proceeds from sale of restricted investments		0
Receivable from customer for property and equipment purchases	0	0
Other	0
Net cash used in investing activities	(471,113)	(555)
Cash flows from financing activities:
Change in book overdrafts	0	0
Borrowings from long-term debt	454,219
Repayments of long-term debt	0	0
Borrowings on revolving lines of credit		0
Repayments on revolving lines of credit		0
Debt issuance costs and other refinancing costs	(7,598)	0
Dividends/distributions	(261)	(340)
Transactions with Parent/affiliates	4,939	(22,106)
Net cash provided by (used in) financing activities	451,299	(22,446)
Net increase (decrease) in cash and cash equivalents	3,433	(24,473)
Cash and cash equivalents, beginning of period	25,326	14,836
Cash and cash equivalents, end of period	28,759	(9,637)
Co-Issuer
Cash flows from operating activities:
Net loss	1,703	(1,004)
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	2,524	2,531
Accretion of asset retirement obligation and receivable	18	16
Non-cash tax benefits	0
Amortization of intangible assets and liabilities, net	146	156
Share-based compensation	7	10
Loss (gain) on sales of assets	0	0
Amortization of deferred financing costs	0	0
Loss on sales of investment securities		0
Loss on foreign exchange	0
Changes in operating assets and liabilities:
Receivables, net	480	2,885
Inventories	4,316	(2,181)
Excess of black lung benefit obligation over trust assets	0	0
Accounts payable and accrued expenses	(3,386)	5,960
Deferred revenue	(2,415)	(1,927)
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	1	4
Other assets and liabilities	(309)	465
Distributions received from subsidiaries	0	0
Net cash provided by operating activities	3,085	6,915
Cash flows from investing activities:
Additions to property, plant and equipment	(35)	(134)
Change in restricted investments and bond collateral and reclamation deposits	5,998	(3)
Net proceeds from sales of assets		0
Proceeds from sale of restricted investments		0
Receivable from customer for property and equipment purchases	0	0
Other	0
Net cash used in investing activities	5,963	(137)
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
Repayments on revolving lines of credit		0
Debt issuance costs and other refinancing costs	0	0
Dividends/distributions	(8,500)	(6,500)
Transactions with Parent/affiliates	154	(16)
Net cash provided by (used in) financing activities	(8,346)	(6,516)
Net increase (decrease) in cash and cash equivalents	702	262
Cash and cash equivalents, beginning of period	3,341	4,545
Cash and cash equivalents, end of period	4,043	4,807
Guarantor Subsidiaries
Cash flows from operating activities:
Net loss	5,803	6,876
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	6,269	5,189
Accretion of asset retirement obligation and receivable	1,278	1,050
Non-cash tax benefits	0
Amortization of intangible assets and liabilities, net	0	0
Share-based compensation	37	681
Loss (gain) on sales of assets	(1)	(133)
Amortization of deferred financing costs	0	13
Loss on sales of investment securities		7
Loss on foreign exchange	0
Changes in operating assets and liabilities:
Receivables, net	(2,738)	(2,467)
Inventories	944	(753)
Excess of black lung benefit obligation over trust assets	0	0
Accounts payable and accrued expenses	7,356	(10)
Deferred revenue	844	1,703
Income tax payable	0	(1,679)
Accrual for workers' compensation	0	0
Asset retirement obligations	(9)	(190)
Accrual for postretirement medical benefits	935	1,478
Pension and SERP obligations	113	177
Other assets and liabilities	(1,616)	(195)
Distributions received from subsidiaries	0	0
Net cash provided by operating activities	19,215	11,747
Cash flows from investing activities:
Additions to property, plant and equipment	(2,609)	(4,224)
Change in restricted investments and bond collateral and reclamation deposits	4	(151)
Net proceeds from sales of assets		309
Proceeds from sale of restricted investments		120
Receivable from customer for property and equipment purchases	0	0
Other	0
Net cash used in investing activities	(2,605)	(3,946)
Cash flows from financing activities:
Change in book overdrafts	(317)	(7)
Borrowings from long-term debt	0
Repayments of long-term debt	(875)	(713)
Borrowings on revolving lines of credit		0
Repayments on revolving lines of credit		0
Debt issuance costs and other refinancing costs	0	0
Dividends/distributions	(18,000)	(8,000)
Transactions with Parent/affiliates	3,434	2,255
Net cash provided by (used in) financing activities	(15,758)	(6,465)
Net increase (decrease) in cash and cash equivalents	852	1,336
Cash and cash equivalents, beginning of period	7,942	5,362
Cash and cash equivalents, end of period	8,794	6,698
Non-Guarantor Subsidiaries
Cash flows from operating activities:
Net loss	726	1,141
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	7,190	6,612
Accretion of asset retirement obligation and receivable	2,183	2,114
Non-cash tax benefits	0
Amortization of intangible assets and liabilities, net	7	8
Share-based compensation	115	1,013
Loss (gain) on sales of assets	39	(101)
Amortization of deferred financing costs	122	149
Loss on sales of investment securities		0
Loss on foreign exchange	0
Changes in operating assets and liabilities:
Receivables, net	6,104	(3,355)
Inventories	(735)	247
Excess of black lung benefit obligation over trust assets	0	0
Accounts payable and accrued expenses	1,327	6,979
Deferred revenue	269	384
Income tax payable	28	1,706
Accrual for workers' compensation	0	0
Asset retirement obligations	(1,343)	(3,017)
Accrual for postretirement medical benefits	345	607
Pension and SERP obligations	(490)	241
Other assets and liabilities	(2,880)	4,081
Distributions received from subsidiaries	0	0
Net cash provided by operating activities	13,007	18,809
Cash flows from investing activities:
Additions to property, plant and equipment	(444)	(786)
Change in restricted investments and bond collateral and reclamation deposits	(395)	(5,883)
Net proceeds from sales of assets		132
Proceeds from sale of restricted investments		5,499
Receivable from customer for property and equipment purchases	(10)	(49)
Other	(60)
Net cash used in investing activities	(909)	(1,087)
Cash flows from financing activities:
Change in book overdrafts	2	827
Borrowings from long-term debt	0
Repayments of long-term debt	(5,364)	(5,860)
Borrowings on revolving lines of credit		6,000
Repayments on revolving lines of credit		(6,000)
Debt issuance costs and other refinancing costs	0	(156)
Dividends/distributions	(16,000)	(5,100)
Transactions with Parent/affiliates	5,067	4,076
Net cash provided by (used in) financing activities	(16,295)	(6,213)
Net increase (decrease) in cash and cash equivalents	(4,197)	11,509
Cash and cash equivalents, beginning of period	24,501	6,867
Cash and cash equivalents, end of period	20,304	18,376
Consolidating Adjustments
Cash flows from operating activities:
Net loss	(8,232)	(7,013)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity in income of subsidiaries	13,319	10,304
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
Loss (gain) on sales of assets	0	0
Amortization of deferred financing costs	0	0
Loss on sales of investment securities		0
Loss on foreign exchange	0
Changes in operating assets and liabilities:
Receivables, net	1,534	3,008
Inventories	0	0
Excess of black lung benefit obligation over trust assets	0	0
Accounts payable and accrued expenses	(8)	(1,482)
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	6,981	0
Distributions received from subsidiaries	(42,500)	(19,600)
Net cash provided by operating activities	(28,906)	(14,783)
Cash flows from investing activities:
Additions to property, plant and equipment	0	0
Change in restricted investments and bond collateral and reclamation deposits	0	0
Net proceeds from sales of assets		0
Proceeds from sale of restricted investments		0
Receivable from customer for property and equipment purchases	0	0
Other	0
Net cash used in investing activities	0	0
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
Repayments on revolving lines of credit		0
Debt issuance costs and other refinancing costs	0	0
Dividends/distributions	42,500	19,600
Transactions with Parent/affiliates	(13,594)	15,791
Net cash provided by (used in) financing activities	28,906	35,391
Net increase (decrease) in cash and cash equivalents	0	20,608
Cash and cash equivalents, beginning of period	0	0
Cash and cash equivalents, end of period	$ 0	$ 20,608