Unaudited Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities
Net income	$ 6,883	$ 5,266
Adjustments to reconcile net income to net cash from operating activities
Accretion of asset retirement obligations	128	123
Depreciation and amortization	4,116	2,438
Amortization of debt issuance costs	14	48
Stock-based compensation	894	551
Deferred income tax expense	1,341	709
Changes in operating assets and liabilities
Accounts receivable	(16,556)	(16,331)
Prepaid expenses	1,196	(1,464)
Inventories	(842)	(74)
Advanced coal royalties	(81)
Other assets and liabilities	144	44
Accounts payable	(4,159)	8,562
Accrued expenses	(1,031)	(3,564)
Net cash from operating activities	(5,891)	3,436
Cash flow from investing activities
Purchases of property, plant and equipment	(8,199)	(12,769)
Proceeds from maturities of investment securities		5,200
Net cash from investing activities	(8,199)	(7,569)
Cash flows from financing activities
Proceeds from borrowings	26,500	6,000
Repayments of borrowings	(17,251)
Repayments of financed insurance payable	(171)	(220)
Payment of debt issuance costs		(257)
Net cash from financing activities	9,078	5,523
Net change in cash and cash equivalents	(5,012)	1,390
Cash and cash equivalents, beginning of period	6,951	5,934
Cash and cash equivalents, end of period	1,939	7,324
Supplemental cash flow information
Cash paid for interest	249	57
Cash paid for taxes
Non-cash investing and financing activities
Capital expenditures included in accounts payable and accrued expenses	4,332	3,172
Financed insurance		789
Additional asset retirement obligations acquired or incurred	$ 43	$ 88