CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 508,874	$ 515,164
Restricted cash	19,376	21,341
Receivables:
Joint interest billings	36,032	21,539
Oil sales		108,995
Other	9,710	3,682
Inventories	53,482	33,281
Prepaid expenses and other	14,409	10,470
Current deferred tax assets	9,275	34,585
Derivatives	1,254	1,061
Total current assets	652,412	750,118
Property and equipment:
Oil and gas properties, net	1,465,723	1,510,312
Other property, net	16,241	15,450
Property and equipment, net	1,481,964	1,525,762
Other assets:
Restricted cash	29,884	29,884
Deferred financing costs, net of accumulated amortization of $19,405 and $13,922 at June 30, 2013 and December 31, 2012, respectively	45,682	50,214
Long-term deferred tax assets	13,653	10,145
Derivatives	2,135
Total assets	2,225,730	2,366,123
Current liabilities:
Accounts payable	63,955	128,855
Accrued liabilities	71,812	41,021
Derivatives	7,000	20,377
Total current liabilities	142,767	190,253
Long-term liabilities:
Long-term debt	900,000	1,000,000
Derivatives	1,202	3,226
Asset retirement obligations	32,602	27,484
Deferred tax liability	129,241	104,137
Other long-term liabilities	18,492	12,117
Total long-term liabilities	1,081,537	1,146,964
Shareholders' equity:
Preference shares, $0.01 par value; 200,000,000 authorized shares; zero issued at June 30, 2013 and December 31, 2012
Common shares, $0.01 par value; 2,000,000,000 authorized shares; 391,867,410 and 391,423,703 issued at June 30, 2013 and December 31, 2012, respectively	3,919	3,914
Additional paid-in capital	1,749,461	1,712,880
Accumulated deficit	(733,898)	(683,176)
Accumulated other comprehensive income	2,968	3,685
Treasury stock, at cost, 4,041,831 and 2,731,941 shares at June 30, 2013 and December 31, 2012, respectively	(21,024)	(8,397)
Total shareholders' equity	1,001,426	1,028,906
Total liabilities and shareholders' equity	$ 2,225,730	$ 2,366,123