Accrued Liabilities (Accrued Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Accounts Payable and Accrued Liabilities, Current [Abstract]
Employee costs	$ 18,941	$ 22,518
Divestiture related costs	18,246	0
Interest payable	17,148	2,647
Taxes	14,211	13,480
Lease operating expenses	8,566	7,346
Hedge settlements	343	1,844
Other	5,254	3,898
Total accrued liabilities	$ 82,709	$ 51,733