SUPPLEMENTAL CONSOLIDATING FINANCIAL INFORMATION - Supplemental Consolidating Statement of Cash Flow Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash flows from operating activities:
Net income (loss)	$ (4,087)	$ (222)
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	14,426	13,289
Accretion of asset retirement obligation and receivable	3,180	2,853
Amortization of intangible assets and liabilities, net	164	162
Non-cash tax benefits	0	(504)
Share-based compensation	2,386	1,902
Loss (gain) on sales of assets	(234)	38
Amortization of deferred financing costs	933	857
Loss (gain) on sales of investment securities	7	(52)
Changes in operating assets and liabilities:
Receivables, net	120	(7,370)
Inventories	(2,687)	(1,495)
Excess of black lung benefit obligation over trust assets	83	327
Accounts payable and accrued expenses	3,245	1,970
Deferred revenue	160	(86)
Income tax payable	27	0
Accrual for workers' compensation	(191)	(80)
Asset retirement obligations	(3,207)	(2,442)
Accrual for postretirement medical benefits	1,985	1,424
Pension and SERP obligations	742	597
Other assets and liabilities	4,164	1,820
Net cash provided by operating activities	21,216	12,988
Cash flows from investing activities:
Distributions received from subsidiaries	0	0
Additions to property, plant and equipment	(5,301)	(4,420)
Change in restricted investments and bond collateral and reclamation deposits	(6,435)	(25,433)
Cash payments related to acquisitions and other		(72,522)
Net proceeds from sales of assets	441	20
Proceeds from sale of restricted investments	5,619	375
Receivable from customer for property and equipment purchases	(49)	(591)
Net cash used in investing activities	(5,725)	(102,571)
Cash flows from financing activities:
Change in book overdrafts	820	(116)
Borrowings from long-term debt	0	119,364
Repayments of long-term debt	(6,573)	(5,445)
Borrowings on revolving lines of credit	6,000	0
Repayments on revolving lines of credit	(6,000)	0
Debt issuance and other refinancing costs	(156)	(4,556)
Dividends/distributions	(340)	(340)
Transactions with Parent/affiliates	0	0
Net cash provided by (used in) financing activities	(6,249)	108,907
Net increase (decrease) in cash and cash equivalents	9,242	19,324
Cash and cash equivalents, beginning of period	31,610	30,783
Cash and cash equivalents, end of period	40,852	50,107
Parent/ Issuer
Cash flows from operating activities:
Net income (loss)	(4,087)	(222)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity in income of subsidiaries	10,304	13,292
Depreciation, depletion, and amortization	94	108
Accretion of asset retirement obligation and receivable	0	0
Amortization of intangible assets and liabilities, net	0	0
Non-cash tax benefits		(504)
Share-based compensation	682	737
Loss (gain) on sales of assets	0	0
Amortization of deferred financing costs	771	604
Loss (gain) on sales of investment securities	0	(52)
Changes in operating assets and liabilities:
Receivables, net	49	(3)
Inventories	0	0
Excess of black lung benefit obligation over trust assets	83	327
Accounts payable and accrued expenses	(8,202)	(3,724)
Deferred revenue	0	0
Income tax payable	0
Accrual for workers' compensation	(191)	(80)
Asset retirement obligations	0	0
Accrual for postretirement medical benefits	(100)	(35)
Pension and SERP obligations	320	271
Other assets and liabilities	(187)	357
Net cash provided by operating activities	(464)	11,076
Cash flows from investing activities:
Distributions received from subsidiaries	19,600	3,500
Additions to property, plant and equipment	(157)	27
Change in restricted investments and bond collateral and reclamation deposits	(398)	(809)
Cash payments related to acquisitions and other		4,000
Net proceeds from sales of assets	0	0
Proceeds from sale of restricted investments	0	375
Receivable from customer for property and equipment purchases	0	0
Net cash used in investing activities	19,045	7,093
Cash flows from financing activities:
Change in book overdrafts	0	140
Borrowings from long-term debt		119,364
Repayments of long-term debt	0	0
Borrowings on revolving lines of credit	0
Repayments on revolving lines of credit	0
Debt issuance and other refinancing costs	0	(4,556)
Dividends/distributions	(340)	(340)
Transactions with Parent/affiliates	(22,106)	(126,524)
Net cash provided by (used in) financing activities	(22,446)	(11,916)
Net increase (decrease) in cash and cash equivalents	(3,865)	6,253
Cash and cash equivalents, beginning of period	14,836	26,141
Cash and cash equivalents, end of period	10,971	32,394
Co-Issuer
Cash flows from operating activities:
Net income (loss)	(1,004)	2,782
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	2,531	2,498
Accretion of asset retirement obligation and receivable	16	15
Amortization of intangible assets and liabilities, net	156	155
Non-cash tax benefits		0
Share-based compensation	10	9
Loss (gain) on sales of assets	0	0
Amortization of deferred financing costs	0	0
Loss (gain) on sales of investment securities	0	0
Changes in operating assets and liabilities:
Receivables, net	2,885	794
Inventories	(2,181)	(359)
Excess of black lung benefit obligation over trust assets	0	0
Accounts payable and accrued expenses	5,960	(297)
Deferred revenue	(1,927)	(2,173)
Income tax payable	0
Accrual for workers' compensation	0	0
Asset retirement obligations	0	0
Accrual for postretirement medical benefits	0	0
Pension and SERP obligations	4	3
Other assets and liabilities	465	(218)
Net cash provided by operating activities	6,915	3,209
Cash flows from investing activities:
Distributions received from subsidiaries	0	0
Additions to property, plant and equipment	(134)	(511)
Change in restricted investments and bond collateral and reclamation deposits	(3)	(2)
Cash payments related to acquisitions and other		0
Net proceeds from sales of assets	0	0
Proceeds from sale of restricted investments	0	0
Receivable from customer for property and equipment purchases	0	0
Net cash used in investing activities	(137)	(513)
Cash flows from financing activities:
Change in book overdrafts	0	(259)
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 and other refinancing costs	0	0
Dividends/distributions	(6,500)	0
Transactions with Parent/affiliates	(16)	44
Net cash provided by (used in) financing activities	(6,516)	(215)
Net increase (decrease) in cash and cash equivalents	262	2,481
Cash and cash equivalents, beginning of period	4,545	6
Cash and cash equivalents, end of period	4,807	2,487
Guarantor Subsidiaries
Cash flows from operating activities:
Net income (loss)	6,876	9,454
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	5,189	3,779
Accretion of asset retirement obligation and receivable	1,050	826
Amortization of intangible assets and liabilities, net	0	0
Non-cash tax benefits		0
Share-based compensation	681	121
Loss (gain) on sales of assets	(133)	0
Amortization of deferred financing costs	13	91
Loss (gain) on sales of investment securities	7	0
Changes in operating assets and liabilities:
Receivables, net	(2,467)	(15,621)
Inventories	(753)	(156)
Excess of black lung benefit obligation over trust assets	0	0
Accounts payable and accrued expenses	(10)	7,679
Deferred revenue	1,703	1,371
Income tax payable	(1,679)
Accrual for workers' compensation	0	0
Asset retirement obligations	(190)	(19)
Accrual for postretirement medical benefits	1,478	873
Pension and SERP obligations	177	103
Other assets and liabilities	(195)	1,590
Net cash provided by operating activities	11,747	10,091
Cash flows from investing activities:
Distributions received from subsidiaries	0	0
Additions to property, plant and equipment	(4,224)	(1,171)
Change in restricted investments and bond collateral and reclamation deposits	(151)	(24,736)
Cash payments related to acquisitions and other		(76,522)
Net proceeds from sales of assets	309	20
Proceeds from sale of restricted investments	120	0
Receivable from customer for property and equipment purchases	0	0
Net cash used in investing activities	(3,946)	(102,409)
Cash flows from financing activities:
Change in book overdrafts	(7)	2
Borrowings from long-term debt		0
Repayments of long-term debt	(713)	(593)
Borrowings on revolving lines of credit	0
Repayments on revolving lines of credit	0
Debt issuance and other refinancing costs	0	0
Dividends/distributions	(8,000)	0
Transactions with Parent/affiliates	2,255	95,462
Net cash provided by (used in) financing activities	(6,465)	94,871
Net increase (decrease) in cash and cash equivalents	1,336	2,553
Cash and cash equivalents, beginning of period	5,362	143
Cash and cash equivalents, end of period	6,698	2,696
Non-Guarantor Subsidiaries
Cash flows from operating activities:
Net income (loss)	1,141	(1,066)
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	6,612	6,904
Accretion of asset retirement obligation and receivable	2,114	2,012
Amortization of intangible assets and liabilities, net	8	7
Non-cash tax benefits		0
Share-based compensation	1,013	1,035
Loss (gain) on sales of assets	(101)	38
Amortization of deferred financing costs	149	162
Loss (gain) on sales of investment securities	0	0
Changes in operating assets and liabilities:
Receivables, net	(3,355)	5,699
Inventories	247	(980)
Excess of black lung benefit obligation over trust assets	0	0
Accounts payable and accrued expenses	6,979	(82)
Deferred revenue	384	716
Income tax payable	1,706
Accrual for workers' compensation	0	0
Asset retirement obligations	(3,017)	(2,423)
Accrual for postretirement medical benefits	607	586
Pension and SERP obligations	241	220
Other assets and liabilities	4,081	91
Net cash provided by operating activities	18,809	12,919
Cash flows from investing activities:
Distributions received from subsidiaries	0	0
Additions to property, plant and equipment	(786)	(2,765)
Change in restricted investments and bond collateral and reclamation deposits	(5,883)	114
Cash payments related to acquisitions and other		0
Net proceeds from sales of assets	132	0
Proceeds from sale of restricted investments	5,499	0
Receivable from customer for property and equipment purchases	(49)	(591)
Net cash used in investing activities	(1,087)	(3,242)
Cash flows from financing activities:
Change in book overdrafts	827	1
Borrowings from long-term debt		0
Repayments of long-term debt	(5,860)	(4,852)
Borrowings on revolving lines of credit	6,000
Repayments on revolving lines of credit	(6,000)
Debt issuance and other refinancing costs	(156)	0
Dividends/distributions	(5,100)	(3,500)
Transactions with Parent/affiliates	4,076	6,711
Net cash provided by (used in) financing activities	(6,213)	(1,640)
Net increase (decrease) in cash and cash equivalents	11,509	8,037
Cash and cash equivalents, beginning of period	6,867	4,493
Cash and cash equivalents, end of period	18,376	12,530
Consolidating Adjustments
Cash flows from operating activities:
Net income (loss)	(7,013)	(11,170)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity in income of subsidiaries	(10,304)	(13,292)
Depreciation, depletion, and amortization	0	0
Accretion of asset retirement obligation and receivable	0	0
Amortization of intangible assets and liabilities, net	0	0
Non-cash tax benefits		0
Share-based compensation	0	0
Loss (gain) on sales of assets	0	0
Amortization of deferred financing costs	0	0
Loss (gain) on sales of investment securities	0	0
Changes in operating assets and liabilities:
Receivables, net	3,008	1,761
Inventories	0	0
Excess of black lung benefit obligation over trust assets	0	0
Accounts payable and accrued expenses	(1,482)	(1,606)
Deferred revenue	0	0
Income tax payable	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	0	0
Net cash provided by operating activities	(15,791)	(24,307)
Cash flows from investing activities:
Distributions received from subsidiaries	(19,600)	(3,500)
Additions to property, plant and equipment	0	0
Change in restricted investments and bond collateral and reclamation deposits	0	0
Cash payments related to acquisitions and other		0
Net proceeds from sales of assets	0	0
Proceeds from sale of restricted investments	0	0
Receivable from customer for property and equipment purchases	0	0
Net cash used in investing activities	(19,600)	(3,500)
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 and other refinancing costs	0	0
Dividends/distributions	19,600	3,500
Transactions with Parent/affiliates	15,791	24,307
Net cash provided by (used in) financing activities	35,391	27,807
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