Summary of Signigicant Accounting Policies (Tables)

6 Months Ended

Jun. 30, 2013

Accounting Policies [Abstract]

Property and Equipment

(in thousands)	June 30, 2013			December 31, 2012
Property and Equipment
Proved oil and gas properties	$	5,354,887		$	5,058,524
Unproved oil and gas properties	93,990			92,579
Furniture, fixtures, and other equipment	42,375			41,690
Less – Accumulated depreciation, depletion, and amortization	(2,968,161		)	(2,847,773		)
Property and Equipment, Net	$	2,523,091		$	2,345,020

Accounts Payable and Accrued Liabilities

	June 30, 2013		December 31, 2012
Trade accounts payable (1)	$	41,145	$	31,128
Accrued operating expenses	17,970		14,647
Accrued payroll costs	8,238		12,297
Asset retirement obligation – current portion	9,520		7,134
Accrued taxes	8,652		5,373
Other payables	2,894		4,799
Total accounts payable and accrued liabilities	$	88,419	$	75,378

(1) Included in “trade accounts payable” are liabilities of approximately $27.9 million and $13.3 million at June 30, 2013 and December 31, 2012, respectively, for outstanding checks.

Roll-forward of our asset retirement obligations

	2013
Asset Retirement Obligation recorded as of January 1	$	86,777
Accretion expense	3,254
Liabilities incurred for new wells and facilities construction	1,214
Reductions due to sold and abandoned wells and facilities	(12,780		)
Revisions in estimates	(113		)
Asset Retirement Obligation as of June 30,	$	78,352