Quarterly report pursuant to Section 13 or 15(d)

Consolidated Statement of Cash Flows Supplemental Disclosures ( Non-cash investing and financing activities) (Details)

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Consolidated Statement of Cash Flows Supplemental Disclosures ( Non-cash investing and financing activities) (Details) (USD $)
In Thousands, unless otherwise specified
6 Months Ended
Jun. 30, 2013
Jun. 30, 2012
Consolidated Statements of Cash Flows Supplemental Disclosures [Abstract]    
Non-cash additions for purchases of property and equipment $ 13,740 $ 12,680
Asset retirement obligation additions to property and equipment 1,066 132
Deferred compensation distribution denominated in shares $ 621 $ 511