Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Cash Flows from Operating Activities:
Net Income	$ 5,413	$ 7,209
Adjustments to reconcile net income to net cash provided by operation activities -
Depreciation, depletion, and amortization	61,685	60,120
Accretion of asset retirement obligation	1,386	1,775
Deferred income taxes	6,248	4,377
Stock-based compensation expenses	2,054	3,015
Other	(3,216)	(3,864)
(Increase) Decrease in accounts receivable	(2,335)	(5,191)
Increase (decrease) in accounts payable and accrued liabilities	6,885	3,085
Increase (decrease) in accrued interest	(8,421)	(8,303)
Net Cash Provided by Operating Activities	69,699	62,223
Cash Flows from Investing Activities:
Additions to property and equipment	(105,589)	(132,981)
Proceeds from the sale of property and equipment	35	999
Net Cash Used in Investing Activities	(105,554)	(131,982)
Cash Flows from Financing Activities:
Proceeds from bank borrowings	115,300	265,600
Payments of bank borrowings	(82,600)	(195,300)
Net proceeds from issuances of common stock	824	946
Purchase of treasury shares	(855)	(1,409)
Net Cash Used in Financing Activities	32,669	69,837
Net Increase (Decrease) in Cash and Cash Equivalents	(3,186)	78
Cash and Cash Equivalents at Beginning of Period	3,277	170
Cash and Cash Equivalents at End of Period	91	248
Supplemental Disclosures of Cash Flows Information:
Cash paid during period for interest, net of amounts capitalized	$ 26,310	$ 24,626