SUPPLEMENTAL CONSOLIDATING FINANCIAL INFORMATION - Supplemental Consolidating Statement of Cash Flow Information (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Cash flows from operating activities:
Net income (loss)	$ (8,127)	$ (13,662)	$ (36,875)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity in income of subsidiaries	0	0	0
Loss on derivative instruments	0	0	3,079
Depreciation, depletion, and amortization	67,231	57,145	45,594
Accretion of asset retirement obligation and receivable	12,681	12,189	10,878
Amortization of intangible assets and liabilities, net	665	658	657
Non-cash tax benefits	(4,892)	0	0
Share-based compensation	5,322	6,040	4,721
Loss (gain) on sales of assets	(74)	528	640
Amortization of deferred financing costs	3,731	4,358	2,515
Other	(1,001)	0	0
Loss on extinguishment of debt	64	1,986	17,030
Gain on sales of investment securities	(3)	(165)	(150)
Changes in operating assets and liabilities:
Receivables, net	(7,636)	(12,855)	5,491
Inventories	(2,512)	(2,164)	(2,125)
Excess of black lung benefit obligation over trust assets	319	1,791	4,319
Accounts payable and accrued expenses	13,579	17,399	4,128
Deferred revenue	(9,078)	(8,198)	(9,918)
Income tax payable	(1)	0	0
Accrual for workers' compensation	(2,069)	(2,096)	1,248
Asset retirement obligations	(9,410)	(6,943)	(6,510)
Accrual for postretirement medical benefits	7,721	6,191	(1,643)
Pension and SERP obligations	2,388	2,802	(1,278)
Other assets and liabilities	11,819	(7,860)	2,934
Net cash provided by (used in) operating activities	80,717	57,144	44,735
Cash flows from investing activities:
Distributions received by subsidiaries	0	0	0
Additions to property, plant and equipment	(28,591)	(21,032)	(27,594)
Change in restricted investments and bond collateral and reclamation deposits	1,434	(33,892)	(5,986)
Cash payments related to acquisitions	0	(72,522)	(4,000)
Net proceeds from sales of assets	902	480	687
Proceeds from sale of restricted investments	8,287	4,106	3,350
Receivable from customer for property and equipment purchases	(389)	(674)	(96)
Other	(3,540)	0	0
Net cash provided by (used in) investing activities	(21,897)	(123,534)	(33,639)
Cash flows from financing activities:
Change in book overdrafts	310	(253)	(724)
Borrowings from long-term debt	0	119,364	142,500
Repayments of long-term debt	(28,088)	(44,846)	(73,566)
Borrowings on revolving lines of credit	7,000	16,500	87,200
Repayments on revolving lines of credit	(7,000)	(16,500)	(105,600)
Debt issuance and other refinancing costs	(182)	(5,688)	(15,019)
Exercise of stock options	0	0	422
Dividends/distributions	(1,360)	(1,360)	(21,301)
Transactions with Parent/affiliates	0	0	0
Net cash provided by (used in) financing activities	(29,320)	67,217	13,912
Net increase (decrease) in cash and cash equivalents	29,500	827	25,008
Cash and cash equivalents, beginning of year	31,610	30,783	5,775
Cash and cash equivalents, end of year	61,110	31,610	30,783
Parent Company [Member]
Cash flows from operating activities:
Net income (loss)	(8,127)	(13,662)	(36,875)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity in income of subsidiaries	(42,347)	(45,762)	(18,508)
Loss on derivative instruments			3,079
Depreciation, depletion, and amortization	354	421	306
Accretion of asset retirement obligation and receivable	0	0	0
Amortization of intangible assets and liabilities, net	0	0	0
Non-cash tax benefits	(4,892)
Share-based compensation	2,437	2,716	1,671
Loss (gain) on sales of assets	0	13	3
Amortization of deferred financing costs	3,165	2,889	1,485
Other	0
Loss on extinguishment of debt	64	1,986	7,873
Gain on sales of investment securities	0	(190)	0
Changes in operating assets and liabilities:
Receivables, net	(18)	147	(158)
Inventories	0	0	0
Excess of black lung benefit obligation over trust assets	319	1,791	4,319
Accounts payable and accrued expenses	(613)	4,981	5,849
Deferred revenue	0	0	0
Income tax payable	0
Accrual for workers' compensation	(2,069)	(2,096)	1,248
Asset retirement obligations	0	0	0
Accrual for postretirement medical benefits	101	(524)	(2,878)
Pension and SERP obligations	1,391	1,286	(4,320)
Other assets and liabilities	(144)	(243)	444
Net cash provided by (used in) operating activities	27,621	(14,276)	(13,062)
Cash flows from investing activities:
Distributions received by subsidiaries	78,000	31,971	23,400
Additions to property, plant and equipment	(737)	(159)	(797)
Change in restricted investments and bond collateral and reclamation deposits	49	(3,248)	(1,714)
Cash payments related to acquisitions		4,000	(4,000)
Net proceeds from sales of assets	0	0	0
Proceeds from sale of restricted investments	0	1,581	0
Receivable from customer for property and equipment purchases	0	0	0
Other	0
Net cash provided by (used in) investing activities	(688)	2,174	(6,511)
Cash flows from financing activities:
Change in book overdrafts	0	0	(146)
Borrowings from long-term debt		119,364	142,500
Repayments of long-term debt	(500)	(23,000)	(2,532)
Borrowings on revolving lines of credit	0	0	0
Repayments on revolving lines of credit	0	0	0
Debt issuance and other refinancing costs	(26)	(5,666)	(6,042)
Exercise of stock options			422
Dividends/distributions	(1,360)	(1,360)	(21,301)
Transactions with Parent/affiliates	(14,557)	(88,541)	(67,458)
Net cash provided by (used in) financing activities	(16,443)	797	45,443
Net increase (decrease) in cash and cash equivalents	10,490	(11,305)	25,870
Cash and cash equivalents, beginning of year	14,836	26,141	271
Cash and cash equivalents, end of year	25,326	14,836	26,141
Co-Issuer [Member]
Cash flows from operating activities:
Net income (loss)	4,215	8,113	5,089
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity in income of subsidiaries	0	0	0
Loss on derivative instruments			0
Depreciation, depletion, and amortization	10,178	10,085	10,175
Accretion of asset retirement obligation and receivable	63	59	55
Amortization of intangible assets and liabilities, net	622	622	621
Non-cash tax benefits	0
Share-based compensation	37	44	32
Loss (gain) on sales of assets	0	0	189
Amortization of deferred financing costs	0	0	(21)
Other	0
Loss on extinguishment of debt	0	0	9,073
Gain on sales of investment securities	0	0	0
Changes in operating assets and liabilities:
Receivables, net	(126)	(151)	1,479
Inventories	(3,114)	709	(1,820)
Excess of black lung benefit obligation over trust assets	0	0	0
Accounts payable and accrued expenses	5,141	(3,209)	(1,063)
Deferred revenue	(8,706)	(8,312)	(8,774)
Income tax payable	0
Accrual for workers' compensation	0	0	0
Asset retirement obligations	0	0	0
Accrual for postretirement medical benefits	0	0	0
Pension and SERP obligations	18	15	(50)
Other assets and liabilities	4,983	(536)	(529)
Net cash provided by (used in) operating activities	13,311	7,439	14,456
Cash flows from investing activities:
Distributions received by subsidiaries	0	0	0
Additions to property, plant and equipment	(790)	(2,067)	(2,119)
Change in restricted investments and bond collateral and reclamation deposits	(8)	(7)	2,581
Cash payments related to acquisitions		0	0
Net proceeds from sales of assets	0	0	0
Proceeds from sale of restricted investments	0	0	0
Receivable from customer for property and equipment purchases	0	0	0
Other	0
Net cash provided by (used in) investing activities	(798)	(2,074)	462
Cash flows from financing activities:
Change in book overdrafts	0	(259)	259
Borrowings from long-term debt		0	0
Repayments of long-term debt	0	0	(46,220)
Borrowings on revolving lines of credit	0	0	1,500
Repayments on revolving lines of credit	0	0	(1,500)
Debt issuance and other refinancing costs	0	0	(9,077)
Exercise of stock options			0
Dividends/distributions	(14,500)	(1,050)	(10,700)
Transactions with Parent/affiliates	783	483	49,946
Net cash provided by (used in) financing activities	(13,717)	(826)	(15,792)
Net increase (decrease) in cash and cash equivalents	(1,204)	4,539	(874)
Cash and cash equivalents, beginning of year	4,545	6	880
Cash and cash equivalents, end of year	3,341	4,545	6
Guarantor Subsidiaries [Member]
Cash flows from operating activities:
Net income (loss)	16,079	37,771	3,463
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity in income of subsidiaries	0	0	0
Loss on derivative instruments			0
Depreciation, depletion, and amortization	27,452	19,571	7,936
Accretion of asset retirement obligation and receivable	4,192	4,038	3,034
Amortization of intangible assets and liabilities, net	0	0	0
Non-cash tax benefits	0
Share-based compensation	914	559	249
Loss (gain) on sales of assets	115	251	59
Amortization of deferred financing costs	49	847	383
Other	(1,001)
Loss on extinguishment of debt	0	0	84
Gain on sales of investment securities	19	0	(75)
Changes in operating assets and liabilities:
Receivables, net	9,871	(20,910)	(4,343)
Inventories	187	(2,389)	134
Excess of black lung benefit obligation over trust assets	0	0	0
Accounts payable and accrued expenses	4,082	18,396	378
Deferred revenue	972	772	(349)
Income tax payable	(1,679)
Accrual for workers' compensation	0	0	0
Asset retirement obligations	(1,971)	(1,198)	(875)
Accrual for postretirement medical benefits	5,620	4,858	0
Pension and SERP obligations	589	709	0
Other assets and liabilities	8,206	1,047	3,839
Net cash provided by (used in) operating activities	73,696	64,322	13,917
Cash flows from investing activities:
Distributions received by subsidiaries	0	0	0
Additions to property, plant and equipment	(17,156)	(8,385)	(2,569)
Change in restricted investments and bond collateral and reclamation deposits	1,766	(27,504)	(3,738)
Cash payments related to acquisitions		(76,522)	0
Net proceeds from sales of assets	534	240	250
Proceeds from sale of restricted investments	788	1,889	1,075
Receivable from customer for property and equipment purchases	0	0	0
Other	(2,500)
Net cash provided by (used in) investing activities	(16,568)	(110,282)	(4,982)
Cash flows from financing activities:
Change in book overdrafts	310	6	(694)
Borrowings from long-term debt		0	0
Repayments of long-term debt	(2,322)	(2,494)	(11,982)
Borrowings on revolving lines of credit	0	0	12,200
Repayments on revolving lines of credit	0	0	(29,100)
Debt issuance and other refinancing costs	0	0	100
Exercise of stock options			0
Dividends/distributions	(44,500)	(19,173)	0
Transactions with Parent/affiliates	(8,036)	72,840	20,684
Net cash provided by (used in) financing activities	(54,548)	51,179	(8,792)
Net increase (decrease) in cash and cash equivalents	2,580	5,219	143
Cash and cash equivalents, beginning of year	5,362	143	0
Cash and cash equivalents, end of year	7,942	5,362	143
Non-Guarantor Subsidiaries [Member]
Cash flows from operating activities:
Net income (loss)	13,072	(4,541)	5,073
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity in income of subsidiaries	0	0	0
Loss on derivative instruments			0
Depreciation, depletion, and amortization	29,247	27,068	27,177
Accretion of asset retirement obligation and receivable	8,426	8,092	7,789
Amortization of intangible assets and liabilities, net	43	36	36
Non-cash tax benefits	0
Share-based compensation	1,934	2,721	2,769
Loss (gain) on sales of assets	(189)	264	389
Amortization of deferred financing costs	517	622	668
Other	0
Loss on extinguishment of debt	0	0	0
Gain on sales of investment securities	(22)	25	(75)
Changes in operating assets and liabilities:
Receivables, net	(4,069)	102	2,263
Inventories	415	(484)	(439)
Excess of black lung benefit obligation over trust assets	0	0	0
Accounts payable and accrued expenses	(9,852)	5,453	3,103
Deferred revenue	(1,344)	(658)	(795)
Income tax payable	1,678
Accrual for workers' compensation	0	0	0
Asset retirement obligations	(7,439)	(5,745)	(5,635)
Accrual for postretirement medical benefits	2,000	1,857	1,235
Pension and SERP obligations	390	792	3,092
Other assets and liabilities	4,124	(10,128)	(392)
Net cash provided by (used in) operating activities	38,931	25,476	46,258
Cash flows from investing activities:
Distributions received by subsidiaries	0	0	0
Additions to property, plant and equipment	(9,908)	(10,421)	(22,109)
Change in restricted investments and bond collateral and reclamation deposits	(373)	(3,133)	(3,115)
Cash payments related to acquisitions		0	0
Net proceeds from sales of assets	368	240	437
Proceeds from sale of restricted investments	7,499	636	2,275
Receivable from customer for property and equipment purchases	(389)	(674)	(96)
Other	(1,040)
Net cash provided by (used in) investing activities	(3,843)	(13,352)	(22,608)
Cash flows from financing activities:
Change in book overdrafts	0	0	(143)
Borrowings from long-term debt		0	0
Repayments of long-term debt	(25,266)	(19,352)	(12,832)
Borrowings on revolving lines of credit	7,000	16,500	73,500
Repayments on revolving lines of credit	(7,000)	(16,500)	(75,000)
Debt issuance and other refinancing costs	(156)	(22)	0
Exercise of stock options			0
Dividends/distributions	(19,000)	(11,748)	(12,700)
Transactions with Parent/affiliates	26,968	21,372	3,394
Net cash provided by (used in) financing activities	(17,454)	(9,750)	(23,781)
Net increase (decrease) in cash and cash equivalents	17,634	2,374	(131)
Cash and cash equivalents, beginning of year	6,867	4,493	4,624
Cash and cash equivalents, end of year	24,501	6,867	4,493
Consolidating Adjustments [Member]
Cash flows from operating activities:
Net income (loss)	(33,366)	(41,343)	(13,625)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity in income of subsidiaries	42,347	45,762	18,508
Loss on derivative instruments			0
Depreciation, depletion, and amortization	0	0	0
Accretion of asset retirement obligation and receivable	0	0	0
Amortization of intangible assets and liabilities, net	0	0	0
Non-cash tax benefits	0
Share-based compensation	0	0	0
Loss (gain) on sales of assets	0	0	0
Amortization of deferred financing costs	0	0	0
Other	0
Loss on extinguishment of debt	0	0	0
Gain on sales of investment securities	0	0	0
Changes in operating assets and liabilities:
Receivables, net	(13,294)	7,957	6,250
Inventories	0	0	0
Excess of black lung benefit obligation over trust assets	0	0	0
Accounts payable and accrued expenses	14,821	(8,222)	(4,139)
Deferred revenue	0	0	0
Income tax payable	0
Accrual for workers' compensation	0	0	0
Asset retirement obligations	0	0	0
Accrual for postretirement medical benefits	0	0	0
Pension and SERP obligations	0	0	0
Other assets and liabilities	(5,350)	2,000	(428)
Net cash provided by (used in) operating activities	(72,842)	(25,817)	(16,834)
Cash flows from investing activities:
Distributions received by subsidiaries	(78,000)	(31,971)	(23,400)
Additions to property, plant and equipment	0	0	0
Change in restricted investments and bond collateral and reclamation deposits	0	0	0
Cash payments related to acquisitions		0	0
Net proceeds from sales of assets	0	0	0
Proceeds from sale of restricted investments	0	0	0
Receivable from customer for property and equipment purchases	0	0	0
Other	0
Net cash provided by (used in) investing activities	0	0	0
Cash flows from financing activities:
Change in book overdrafts	0	0	0
Borrowings from long-term debt		0	0
Repayments of long-term debt	0	0	0
Borrowings on revolving lines of credit	0	0	0
Repayments on revolving lines of credit	0	0	0
Debt issuance and other refinancing costs	0	0	0
Exercise of stock options			0
Dividends/distributions	78,000	31,971	23,400
Transactions with Parent/affiliates	(5,158)	(6,154)	(6,566)
Net cash provided by (used in) financing activities	72,842	25,817	16,834
Net increase (decrease) in cash and cash equivalents	0	0	0
Cash and cash equivalents, beginning of year	0	0	0
Cash and cash equivalents, end of year	$ 0	$ 0	$ 0