SUPPLEMENTAL CONSOLIDATING FINANCIAL INFORMATION - Supplemental Consolidating Statement of Cash Flow Information (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Cash flows from operating activities:
Net loss	$ (131,318)	$ (2,884)
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	68,713	47,257
Accretion of asset retirement obligation and receivable	16,257	9,507
Non-cash tax benefits	(711)	0
Amortization of intangible assets and liabilities, net	385	498
Share-based compensation	3,456	4,594
Loss (gain) on sales of assets	114	(321)
Amortization of deferred financing costs	2,365	2,790
Loss on sales of investment securities		(25)
Loss on extinguishment of debt	12,648	64
Loss (gain) on sales of investment securities	36	(25)
Derivative loss	29,621	0
Loss on foreign exchange	5,883	0
Pension settlement accounting	814	0
Income from equity affiliates	(2,060)	0
Distributions from equity affiliates	2,948	0
Changes in operating assets and liabilities:
Receivables, net	(24,520)	(8,491)
Inventories	55,399	(1,600)
Excess of black lung benefit obligation over trust assets	2,093	53
Deferred income tax	3,344	0
Accounts payable and accrued expenses	6,377	12,457
Deferred revenue	(9,140)	(8,275)
Income tax payable	556	(26)
Accrual for workers' compensation	(178)	(359)
Asset retirement obligations	(5,881)	(6,888)
Accrual for postretirement medical benefits	2,163	6,030
Pension and SERP obligations	(1,004)	2,273
Other assets and liabilities	(149)	1,815
Distributions received from subsidiaries	0	0
Net cash provided by operating activities	38,211	58,469
Cash flows from investing activities:
Additions to property, plant and equipment	(35,646)	(20,223)
Change in restricted investments and bond collateral and reclamation deposits	(41,795)	(9,652)
Cash payments related to Canadian Acquisition	(322,637)	0
Cash acquired in related to Canadian Acquisition, net	8,103	0
Net proceeds from sales of assets	38,085	604
Proceeds from sale of investments	7,279	7,927
Increase in loan and lease receivables	(2,514)	0
Receipts from loan and lease receivables	5,057	0
Receivable from customer for property and equipment purchases	55	(1)
Investment of common shares	0
Other	(602)	0
Net cash used in investing activities	(344,615)	(21,345)
Cash flows from financing activities:
Change in book overdrafts	(317)	20
Borrowings from long-term debt	454,219	0
Repayments of long-term debt	(110,792)	(22,065)
Borrowings on revolving lines of credit	15,000	7,000
Repayments on revolving lines of credit	(15,000)	(7,000)
Debt issuance costs and other refinancing costs	(27,827)	(182)
Dividends/distributions	(664)	(1,020)
Proceeds from Issuance of Common Stock	56,473	0
Exercise of stock options	417	0
Transactions with Parent/affiliates	0	0
Net cash provided by (used in) financing activities	371,509	(23,247)
Effect of foreign exchange rates on cash	(2,525)	0
Net increase (decrease) in cash and cash equivalents	62,580	13,877
Cash and cash equivalents, beginning of period	61,110	31,610
Cash and cash equivalents, end of period	123,690	45,487
Parent/ Issuer
Cash flows from operating activities:
Net loss	(131,318)	(2,884)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity in income of subsidiaries	47,274	(41,732)
Depreciation, depletion, and amortization	225	280
Accretion of asset retirement obligation and receivable	0	0
Non-cash tax benefits	(711)
Amortization of intangible assets and liabilities, net	0	0
Share-based compensation	2,256	2,233
Loss (gain) on sales of assets	0	0
Amortization of deferred financing costs	620	2,353
Loss on sales of investment securities		0
Loss on extinguishment of debt	64	64
Loss (gain) on sales of investment securities	0
Derivative loss	0
Loss on foreign exchange	5,382
Pension settlement accounting	0
Income from equity affiliates	0
Distributions from equity affiliates	0
Changes in operating assets and liabilities:
Receivables, net	(240)	(652)
Inventories	0	0
Excess of black lung benefit obligation over trust assets	2,093	53
Deferred income tax	0
Accounts payable and accrued expenses	126	(8,157)
Deferred revenue	0	0
Income tax payable	0	0
Accrual for workers' compensation	(179)	(359)
Asset retirement obligations	0	0
Accrual for postretirement medical benefits	(1,428)	118
Pension and SERP obligations	256	1,041
Other assets and liabilities	(7,996)	(240)
Distributions received from subsidiaries	92,100	50,800
Net cash provided by operating activities	8,524	2,918
Cash flows from investing activities:
Additions to property, plant and equipment	16	(520)
Change in restricted investments and bond collateral and reclamation deposits	(48,244)	91
Cash payments related to Canadian Acquisition	(282,788)
Cash acquired in related to Canadian Acquisition, net	0
Net proceeds from sales of assets	0	0
Proceeds from sale of investments	0	0
Increase in loan and lease receivables	0
Receipts from loan and lease receivables	0
Receivable from customer for property and equipment purchases	0	0
Investment of common shares	(2,992)
Other	0
Net cash used in investing activities	(334,008)	(429)
Cash flows from financing activities:
Change in book overdrafts	0	0
Borrowings from long-term debt	454,219
Repayments of long-term debt	(1,015)	(500)
Borrowings on revolving lines of credit	0	0
Repayments on revolving lines of credit	0	0
Debt issuance costs and other refinancing costs	(16,168)	(26)
Dividends/distributions	(664)	(1,020)
Proceeds from Issuance of Common Stock	56,473
Exercise of stock options	417
Transactions with Parent/affiliates	(97,859)	(7,132)
Net cash provided by (used in) financing activities	395,403	(8,678)
Effect of foreign exchange rates on cash	0
Net increase (decrease) in cash and cash equivalents	69,919	(6,189)
Cash and cash equivalents, beginning of period	25,326	14,836
Cash and cash equivalents, end of period	95,245	8,647
Co-Issuer
Cash flows from operating activities:
Net loss	(34,357)	8,913
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	7,513	7,632
Accretion of asset retirement obligation and receivable	51	48
Non-cash tax benefits	0
Amortization of intangible assets and liabilities, net	354	467
Share-based compensation	20	30
Loss (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	29,621
Loss on foreign exchange	0
Pension settlement accounting	0
Income from equity affiliates	0
Distributions from equity affiliates	0
Changes in operating assets and liabilities:
Receivables, net	971	(1,651)
Inventories	2,736	(1,020)
Excess of black lung benefit obligation over trust assets	0	0
Deferred income tax	0
Accounts payable and accrued expenses	(2,264)	4,314
Deferred revenue	(7,167)	(6,608)
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	4	13
Other assets and liabilities	(5,282)	(453)
Distributions received from subsidiaries	0	0
Net cash provided by operating activities	(7,800)	11,685
Cash flows from investing activities:
Additions to property, plant and equipment	(419)	(715)
Change in restricted investments and bond collateral and reclamation deposits	2,598	(6)
Cash payments related to Canadian Acquisition	0
Cash acquired in related to Canadian Acquisition, net	0
Net proceeds from sales of assets	0	0
Proceeds from sale of investments	0	0
Increase in loan and lease receivables	0
Receipts from loan and lease receivables	0
Receivable from customer for property and equipment purchases	0	0
Investment of common shares	0
Other	0
Net cash used in investing activities	2,179	(721)
Cash flows from financing activities:
Change in book overdrafts	493	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)	(14,500)
Proceeds from Issuance of Common Stock	0
Exercise of stock options	0
Transactions with Parent/affiliates	10,287	(102)
Net cash provided by (used in) financing activities	2,280	(14,602)
Effect of foreign exchange rates on cash	0
Net increase (decrease) in cash and cash equivalents	(3,341)	(3,638)
Cash and cash equivalents, beginning of period	3,341	4,545
Cash and cash equivalents, end of period	0	907
Guarantor Subsidiaries
Cash flows from operating activities:
Net loss	(12,004)	29,265
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	60,975	39,345
Accretion of asset retirement obligation and receivable	16,206	9,460
Non-cash tax benefits	0
Amortization of intangible assets and liabilities, net	31	32
Share-based compensation	1,180	2,333
Loss (gain) on sales of assets	114	(321)
Amortization of deferred financing costs	1,745	441
Loss on sales of investment securities		(26)
Loss on extinguishment of debt	12,584	0
Loss (gain) on sales of investment securities	36
Derivative loss	0
Loss on foreign exchange	501
Pension settlement accounting	814
Income from equity affiliates	(2,060)
Distributions from equity affiliates	2,948
Changes in operating assets and liabilities:
Receivables, net	(31,512)	(7,426)
Inventories	52,663	(580)
Excess of black lung benefit obligation over trust assets	0	0
Deferred income tax	(750)
Accounts payable and accrued expenses	14,361	14,783
Deferred revenue	(1,973)	(1,667)
Income tax payable	556	(26)
Accrual for workers' compensation	1	0
Asset retirement obligations	(5,882)	(6,887)
Accrual for postretirement medical benefits	3,567	5,624
Pension and SERP obligations	(1,273)	1,191
Other assets and liabilities	7,849	2,971
Distributions received from subsidiaries	0	0
Net cash provided by operating activities	120,677	88,512
Cash flows from investing activities:
Additions to property, plant and equipment	(35,244)	(18,985)
Change in restricted investments and bond collateral and reclamation deposits	3,851	(9,735)
Cash payments related to Canadian Acquisition	(39,849)
Cash acquired in related to Canadian Acquisition, net	8,103
Net proceeds from sales of assets	38,085	604
Proceeds from sale of investments	7,279	7,927
Increase in loan and lease receivables	(2,514)
Receipts from loan and lease receivables	5,057
Receivable from customer for property and equipment purchases	55	(1)
Investment of common shares	2,992
Other	(602)
Net cash used in investing activities	(12,787)	(20,190)
Cash flows from financing activities:
Change in book overdrafts	1,188	20
Borrowings from long-term debt	0
Repayments of long-term debt	(109,777)	(21,558)
Borrowings on revolving lines of credit	15,000	7,000
Repayments on revolving lines of credit	(15,000)	(7,000)
Debt issuance costs and other refinancing costs	(11,659)	(156)
Dividends/distributions	(83,600)	(23,500)
Proceeds from Issuance of Common Stock	0
Exercise of stock options	0
Transactions with Parent/affiliates	99,006	(307)
Net cash provided by (used in) financing activities	(104,842)	(45,501)
Effect of foreign exchange rates on cash	(2,525)
Net increase (decrease) in cash and cash equivalents	523	22,821
Cash and cash equivalents, beginning of period	27,451	10,237
Cash and cash equivalents, end of period	27,974	33,058
Non-Guarantor Subsidiaries
Cash flows from operating activities:
Net loss	512	(2,561)
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)
Non-cash tax benefits	0
Amortization of intangible assets and liabilities, net	0	(1)
Share-based compensation	0	(2)
Loss (gain) on sales of assets	0	0
Amortization of deferred financing costs	0	(4)
Loss on sales of investment securities		1
Loss on extinguishment of debt	0	0
Loss (gain) on sales of investment securities	0
Derivative loss	0
Loss on foreign exchange	0
Pension settlement accounting	0
Income from equity affiliates	0
Distributions from equity affiliates	0
Changes in operating assets and liabilities:
Receivables, net	4,719	(3,248)
Inventories	0	0
Excess of black lung benefit obligation over trust assets	0	0
Deferred income tax	0
Accounts payable and accrued expenses	(5,820)	4,472
Deferred revenue	0	0
Income tax payable	0	0
Accrual for workers' compensation	0	0
Asset retirement obligations	1	(1)
Accrual for postretirement medical benefits	24	288
Pension and SERP obligations	9	28
Other assets and liabilities	(1,299)	(464)
Distributions received from subsidiaries	0	0
Net cash provided by operating activities	(1,854)	(1,493)
Cash flows from investing activities:
Additions to property, plant and equipment	1	(3)
Change in restricted investments and bond collateral and reclamation deposits	0	(2)
Cash payments related to Canadian Acquisition	0
Cash acquired in related to Canadian Acquisition, net	0
Net proceeds from sales of assets	0	0
Proceeds from sale of investments	0	0
Increase in loan and lease receivables	0
Receipts from loan and lease receivables	0
Receivable from customer for property and equipment purchases	0	0
Investment of common shares	0
Other	0
Net cash used in investing activities	1	(5)
Cash flows from financing activities:
Change in book overdrafts	0	0
Borrowings from long-term debt	0
Repayments of long-term debt	0	(7)
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	(12,800)
Proceeds from Issuance of Common Stock	0
Exercise of stock options	0
Transactions with Parent/affiliates	(670)	15,188
Net cash provided by (used in) financing activities	(670)	2,381
Effect of foreign exchange rates on cash	0
Net increase (decrease) in cash and cash equivalents	(2,523)	883
Cash and cash equivalents, beginning of period	4,992	1,992
Cash and cash equivalents, end of period	2,469	2,875
Consolidating Adjustments
Cash flows from operating activities:
Net loss	45,849	(35,617)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity in income of subsidiaries	(47,274)	41,732
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 extinguishment of debt	0	0
Loss (gain) on sales of investment securities	0
Derivative loss	0
Loss on foreign exchange	0
Pension settlement accounting	0
Income from equity affiliates	0
Distributions from equity affiliates	0
Changes in operating assets and liabilities:
Receivables, net	1,542	4,486
Inventories	0	0
Excess of black lung benefit obligation over trust assets	0	0
Deferred income tax	4,094
Accounts payable and accrued expenses	(26)	(2,955)
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	6,579	1
Distributions received from subsidiaries	(92,100)	(50,800)
Net cash provided by operating activities	(81,336)	(43,153)
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
Cash payments related to Canadian Acquisition	0
Cash acquired in related to Canadian Acquisition, net	0
Net proceeds from sales of assets	0	0
Proceeds from sale of investments	0	0
Increase in loan and lease receivables	0
Receipts from loan and lease receivables	0
Receivable from customer for property and equipment purchases	0	0
Investment of common shares	0
Other	0
Net cash used in investing activities	0	0
Cash flows from financing activities:
Change in book overdrafts	(1,998)	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	92,100	50,800
Proceeds from Issuance of Common Stock	0
Exercise of stock options	0
Transactions with Parent/affiliates	(10,764)	(7,647)
Net cash provided by (used in) financing activities	79,338	43,153
Effect of foreign exchange rates on cash	0
Net increase (decrease) in cash and cash equivalents	(1,998)	0
Cash and cash equivalents, beginning of period	0	0
Cash and cash equivalents, end of period	$ (1,998)	$ 0