CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Supplemental Disclosures of Cash Flow Information Cash payments for:
Interest, net of capitalized interest	$ 215	$ 488	$ 541
Other cash flow information:
Equipment exchange credit for new equipment purchase	$ 2,923	$ 88	$ 5,144