Condensed Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Current assets:
Cash and cash equivalents	$ 30,571	$ 31,997
Restricted cash	164,042	155,925
Accounts receivable, net:
Oil and natural gas	49,133	88,518
Joint interest	130,183	170,918
Interest and other	28,392	28,488
Inventory	8,101	8,345
Derivative financial instruments	171,182	164,002
Other	21,246	29,815
Total current assets	602,850	678,008
Equity investments	295,064	302,833
Oil and natural gas properties (full cost accounting method):
Unproved oil and natural gas properties and development costs not being amortized	623,268	667,342
Proved developed and undeveloped oil and natural gas properties	3,320,977	3,392,146
Accumulated depletion	(1,742,681)	(1,657,165)
Oil and natural gas properties, net	2,201,564	2,402,323
Gas gathering assets	136,740	136,203
Accumulated depreciation and amortization	(30,767)	(29,104)
Gas gathering assets, net	105,973	107,099
Office, field, and other equipment, net	41,228	42,384
Deferred financing costs, net	28,101	29,622
Derivative financial instruments	10,073	11,034
Goodwill	218,256	218,256
Other assets	28	28
Total assets	3,503,137	3,791,587
Current liabilities:
Accounts payable and accrued liabilities	126,790	117,968
Revenues and royalties payable	117,657	148,926
Accrued interest payable	3,713	17,973
Current portion of asset retirement obligations	732	732
Income taxes payable	0	0
Derivative financial instruments	3,447	1,800
Total current liabilities	252,339	287,399
Long-term debt	1,918,106	1,887,828
Deferred income taxes	0	0
Derivative financial instruments	852	0
Asset retirement obligations and other long-term liabilities	59,006	58,028
Commitments and contingencies
Shareholders' equity:
Preferred stock, $0.001 par value; 10,000,000 authorized shares; none issued and outstanding	0	0
Common stock, $0.001 par value; 350,000,000 authorized shares; 217,197,701 shares issued and 216,658,480 shares outstanding at March 31, 2012; 217,245,504 shares issued and 216,706,283 shares outstanding at December 31, 2011	215	215
Additional paid-in capital	3,185,877	3,181,063
Accumulated deficit	(1,905,779)	(1,615,467)
Treasury stock, at cost; 539,221 shares at March 31, 2012 and December 31, 2011	(7,479)	(7,479)
Total shareholders' equity	1,272,834	1,558,332
Total liabilities and shareholders' equity	$ 3,503,137	$ 3,791,587