Condensed Consolidated Statement of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Cash flows from operating activities:
Net income (loss)	$ (18,041)us-gaap_NetIncomeLoss	$ 169,953us-gaap_NetIncomeLoss
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation, depletion and amortization	118,478	91,272
Gain on sale of properties	0us-gaap_GainLossOnSaleOfProperties	(183,393)us-gaap_GainLossOnSaleOfProperties
Impairment of oil and gas properties	5,321us-gaap_ImpairmentOfOilAndGasProperties	762us-gaap_ImpairmentOfOilAndGasProperties
Deferred income taxes	(7,376)us-gaap_DeferredIncomeTaxExpenseBenefit	98,753us-gaap_DeferredIncomeTaxExpenseBenefit
Derivative instruments	(47,072)	17,603
Stock-based compensation expenses	7,606us-gaap_ShareBasedCompensation	4,505us-gaap_ShareBasedCompensation
Deferred financing costs amortization and other	1,655oas_DebtDiscountAmortizationAndOther	1,487oas_DebtDiscountAmortizationAndOther
Working capital and other changes:
Change in accounts receivable	63,313	(9,275)
Change in inventory	(602)us-gaap_IncreaseDecreaseInInventories	790us-gaap_IncreaseDecreaseInInventories
Change in prepaid expenses	1,892	(14,259)
Change in other current assets	5,539	(29)
Change in other assets	0	(1,593)
Change in accounts payable and accrued liabilities	(42,341)	29,007
Change in other current liabilities	0	2,766
Change in other liabilities	(11)	(82)
Net cash provided by operating activities	88,361	208,267
Cash flows from investing activities:
Capital expenditures	(359,113)	(280,895)
Proceeds from sale of properties	0	321,943
Costs related to sale of properties	0	(2,010)
Derivative settlements	109,259	(2,239)
Advances from joint interest partners	(828)	(1,898)
Net cash provided by (used in) investing activities	(250,682)	34,901
Cash flows from financing activities:
Proceeds from sale of common stock	463,218	0
Proceeds from revolving credit facility	145,000	0
Principal payments on revolving credit facility	(480,000)	(275,570)
Purchases of treasury stock	(1,520)	(3,025)
Other	0	(176)
Net cash provided by (used in) financing activities	126,698	(278,771)
Decrease in cash and cash equivalents	(35,623)	(35,603)
Cash and cash equivalents:
Beginning of period	45,811	91,901
End of period	10,188	56,298
Supplemental non-cash transactions:
Change in accrued capital expenditures	(90,189)	39,516
Change in asset retirement obligations	$ 1,413oas_NonCashAssetRetirementObligations	$ (128)oas_NonCashAssetRetirementObligations

The total of the component of interest expense representing the noncash expenses charged against earnings in the period to amortize the long-term deferred financing costs and other income (expense) included in net income that results in no cash inflows or outflows in the period. Includes noncash adjustments to reconcile net income (loss) to cash provided by (used in) operating activities that are not separately disclosed.

No definition available.