CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 497,289	$ 515,164
Restricted cash	20,455	21,341
Receivables:
Joint interest billings	27,747	21,539
Oil sales	106,707	108,995
Other	2,813	3,682
Inventories	30,120	33,281
Prepaid expenses and other	10,768	10,470
Current deferred tax assets	27,806	34,585
Derivatives	3,204	1,061
Total current assets	726,909	750,118
Property and equipment:
Oil and gas properties, net	1,527,267	1,510,312
Other property, net	15,046	15,450
Property and equipment, net	1,542,313	1,525,762
Other assets:
Restricted cash	29,884	29,884
Deferred financing costs, net of accumulated amortization of $16,619 and $13,922, respectively	47,484	50,214
Long-term deferred tax assets	12,088	10,145
Total assets	2,358,678	2,366,123
Current liabilities:
Accounts payable	48,785	128,855
Accrued liabilities	58,340	41,021
Derivatives	18,004	20,377
Total current liabilities	125,129	190,253
Long-term liabilities:
Long-term debt	1,000,000	1,000,000
Derivatives	3,785	3,226
Asset retirement obligations	29,957	27,484
Deferred tax liability	113,585	104,137
Other long-term liabilities	18,725	12,117
Total long-term liabilities	1,166,052	1,146,964
Shareholders' equity:
Preference shares, $0.01 par value; 200,000,000 authorized shares; zero issued at March 31, 2013 and December 31, 2012
Common shares, $0.01 par value; 2,000,000,000 authorized shares; 391,447,003 and 391,423,703 issued at March 31, 2013 and December 31, 2012, respectively	3,914	3,914
Additional paid-in capital	1,731,819	1,712,880
Accumulated deficit	(663,082)	(683,176)
Accumulated other comprehensive income	3,326	3,685
Treasury stock, at cost, 2,860,229 and 2,731,941 shares at March 31, 2013 and December 31, 2012, respectively	(8,480)	(8,397)
Total shareholders' equity	1,067,497	1,028,906
Total liabilities and shareholders' equity	$ 2,358,678	$ 2,366,123