Condensed Consolidated Balance Sheet (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
ASSETS
Cash and cash equivalents	$ 280,303	$ 470,872
Short-term investments	126,213	19,994
Accounts receivable - oil and gas revenues	104,965	52,164
Accounts receivable - joint interest partners	83,630	67,268
Inventory	21,142	3,543
Prepaid expenses	4,030	2,140
Advances to joint interest partners	4,025	3,935
Derivative instruments	17,320
Deferred income taxes		3,233
Other current assets	78	491
Total current assets	641,706	623,640
Property, plant and equipment
Oil and gas properties (successful efforts method)	2,079,016	1,235,357
Other property and equipment	45,261	20,859
Less: accumulated depreciation, depletion, amortization and impairment	(320,478)	(176,261)
Total property, plant and equipment, net	1,803,799	1,079,955
Derivative instruments	10,047	4,362
Deferred costs and other assets	25,349	19,425
Total assets	2,480,901	1,727,382
LIABILITIES AND STOCKHOLDERS' EQUITY
Accounts payable	30,954	12,207
Advances from joint interest partners	26,572	9,064
Revenues and production taxes payable	64,091	19,468
Accrued liabilities	200,544	119,692
Accrued interest payable	22,481	15,774
Derivative instruments	1,273	5,907
Deferred income taxes	3,782
Other current liabilities	5,256	472
Total current liabilities	354,953	182,584
Long-term debt	1,200,000	800,000
Asset retirement obligations	20,529	13,075
Derivative instruments	360	3,505
Deferred income taxes	152,617	92,983
Other liabilities	2,078	997
Total liabilities	1,730,537	1,093,144
Commitments and contingencies (Note 12)
Stockholders' equity
Common stock, $0.01 par value; 300,000,000 shares authorized; 93,435,593 issued and 93,369,468 outstanding at September 30, 2012; 92,483,393 issued and 92,460,914 outstanding at December 31, 2011	923	921
Treasury stock, at cost; 66,125 and 22,479 shares at September 30, 2012 and December 31, 2011, respectively	(1,901)	(602)
Additional paid-in-capital	653,999	647,374
Retained earnings (deficit)	97,343	(13,455)
Total stockholders' equity	750,364	634,238
Total liabilities and stockholders' equity	$ 2,480,901	$ 1,727,382