Condensed Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income/(loss)	$ (177)	$ 8,974
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	10,212	11,092
Accretion on asset retirement obligations	589	438
Accretion on interest-free debt	57	54
Amortization of deferred revenue	(302)	(254)
Amortization of advance royalties	25	81
Amortization of debt issuance costs	269	269
Amortization of actuarial gain	(36)	(74)
Equity in net (income)/loss of unconsolidated affiliate	1,372	(2,065)
Loss on retirement of advance royalties	10
(Gain)/loss on sale/disposal of assets-net	925	(1,158)
Equity-based compensation	283	274
Changes in assets and liabilities:
Accounts receivable	(2,734)	9,926
Inventories	3,706	(12,240)
Advance royalties	(393)	61
Prepaid expenses and other assets	347	1,215
Accounts payable	(947)	125
Accrued expenses and other liabilities	(2,361)	491
Asset retirement obligations	(341)	(299)
Postretirement benefits	99	147
Net cash provided by operating activities	10,603	17,057
CASH FLOWS FROM INVESTING ACTIVITIES:
Additions to property, plant, and equipment	(6,089)	(25,438)
Proceeds from sales of property, plant, and equipment	523	1,088
Principal payments received on notes receivable		1,785
Cash paid from issuance of notes receivable		(4,590)
Investment in unconsolidated affiliates	(677)	(114)
Net cash used in investing activities	(6,243)	(27,269)
CASH FLOWS FROM FINANCING ACTIVITIES:
Borrowings on line of credit	39,700	77,400
Repayments on line of credit	(35,470)	(52,850)
Repayments on long-term debt	(1,229)	(650)
Distributions to unitholders	(7,097)	(13,575)
General partner's contributions	2	1
Net settlement of employee withholding taxes on unit awards vested	(25)
Payment of offering costs		(7)
Net cash (used in)/provided by financing activities	(4,119)	10,319
NET INCREASE IN CASH AND CASH EQUIVALENTS	241	107
CASH AND CASH EQUIVALENTS-Beginning of period	461	449
CASH AND CASH EQUIVALENTS-End of period	$ 702	$ 556