2.2.0.7 false Consolidated Balance Sheets (Unaudited) (USD $) 0110 - Statement - Consolidated Balance Sheets (Unaudited) true false In Thousands false false 1 USD false false USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 USDEPS Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 $ false 2 USD false false USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 $ 4 CURRENT ASSETS: 2 us-gaap_AssetsCurrentAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 5 Cash and cash equivalents 3 us-gaap_CashAndCashEquivalentsAtCarryingValue us-gaap true debit instant No definition available. false false false false false false false false false false false verboselabel false 1 true true false false 15521000 15521 false false false 2 true true false false 11960000 11960 false false false xbrli:monetaryItemType monetary Includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the Entity may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months. Compensating balance arrangements that do not legally restrict the withdrawal or usage of cash amounts may be reported as Cash and Cash Equivalents, while legally restricted deposits held as compensating balances against borrowing arrangements, contracts entered into with others, or company statements of intention with regard to particular deposits should not be reported as cash and cash equivalents. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 7, 26 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 8, 9 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 7 -Footnote 1 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 1 -Article 5 false 6 Accounts receivable trade, net 3 us-gaap_AccountsReceivableNetCurrent us-gaap true debit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 169109000 169109 false false false 2 false true false false 152082000 152082 false false false xbrli:monetaryItemType monetary Amount due from customers or clients, within one year of the balance sheet date (or the normal operating cycle, whichever is longer), for goods or services (including trade receivables) that have been delivered or sold in the normal course of business, reduced to the estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 3 -Subparagraph a(1) -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 4 -Article 5 false 7 Derivative assets 3 us-gaap_CommodityContractAssetCurrent us-gaap true debit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 7440000 7440 false false false 2 false true false false 4723000 4723 false false false xbrli:monetaryItemType monetary Carrying amount as of the balance sheet date of the asset arising from commodity contracts such as futures contracts tied to the movement of a particular commodity, which are expected to be converted into cash or otherwise disposed of within a year or the normal operating cycle, if longer. No authoritative reference available. false 8 Prepaid expenses and other 3 us-gaap_OtherAssetsCurrent us-gaap true debit instant No definition available. false false false false false false false false false false false totallabel false 1 false true false false 9593000 9593 false false false 2 false true false false 7260000 7260 false false false xbrli:monetaryItemType monetary Aggregate carrying amount, as of the balance sheet date, of current assets not separately presented elsewhere in the balance sheet. Current assets are expected to be realized or consumed within one year (or the normal operating cycle, if longer). Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 8 -Article 5 true 9 Total current assets 3 us-gaap_AssetsCurrent us-gaap true debit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 201663000 201663 false false false 2 false true false false 176025000 176025 false false false xbrli:monetaryItemType monetary Sum of the carrying amounts as of the balance sheet date of all assets that are expected to be realized in cash, sold, or consumed within one year (or the normal operating cycle, if longer). Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 9 -Article 5 false 11 Oil and gas properties, successful efforts method: 3 us-gaap_OilAndGasPropertySuccessfulEffortMethodGrossAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 12 Proved properties 4 us-gaap_ProvedOilAndGasPropertySuccessfulEffortMethod us-gaap true debit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 5152879000 5152879 false false false 2 false true false false 4870688000 4870688 false false false xbrli:monetaryItemType monetary Oil and Gas properties with proved reserves under the successful effort method. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 19 -Paragraph 11 -Subparagraph a false 13 Unproved properties 4 us-gaap_UnprovedOilAndGasPropertySuccessfulEffortMethod us-gaap true debit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 123213000 123213 false false false 2 false true false false 100706000 100706 false false false xbrli:monetaryItemType monetary Oil and Gas properties with unproved reserves under the successful effort method. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 19 -Paragraph 11 -Subparagraph a Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 19 -Paragraph 147, 148 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 19 -Paragraph 59N false 14 Other property and equipment 3 us-gaap_PropertyPlantAndEquipmentOther us-gaap true debit instant No definition available. false false false false false false false false false false false totallabel false 1 false true false false 94593000 94593 false false false 2 false true false false 100833000 100833 false false false xbrli:monetaryItemType monetary This element represents capitalized assets classified as property, plant and equipment not otherwise defined in the taxonomy. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 12 -Paragraph 5 true 15 Total property and equipment 3 us-gaap_PropertyPlantAndEquipmentGross us-gaap true debit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 5370685000 5370685 false false false 2 false true false false 5072227000 5072227 false false false xbrli:monetaryItemType monetary Carrying amount at the balance sheet date for long-lived physical assets used in the normal conduct of business and not intended for resale. This can include land, physical structures, machinery, vehicles, furniture, computer equipment, construction in progress, and similar items. Amount does not include depreciation. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 12 -Paragraph 5 false 16 Less accumulated depreciation, depletion and amortization 3 us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment us-gaap true credit instant No definition available. false false false false false false false false false false true negatedtotal false 1 false true false false -1450636000 -1450636 false false false 2 false true false false -1274121000 -1274121 false false false xbrli:monetaryItemType monetary The cumulative amount of depreciation, depletion and amortization (related to property, plant and equipment, but not including land) that has been recognized in the income statement. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 12 -Paragraph 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 12 -Paragraph 5 -Subparagraph c Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 14 -Article 5 true 17 Total property and equipment, net 3 us-gaap_PropertyPlantAndEquipmentNet us-gaap true debit instant No definition available. false false false false false false false false false false false totallabel false 1 false true false false 3920049000 3920049 false false false 2 false true false false 3798106000 3798106 false false false xbrli:monetaryItemType monetary Tangible assets that are held by an entity for use in the production or supply of goods and services, for rental to others, or for administrative purposes and that are expected to provide economic benefit for more than one year; net of accumulated depreciation. Examples include land, buildings, and production equipment. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 13 -Subparagraph a -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 12 -Paragraph 5 -Subparagraph b, c Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 8 -Article 7 true 18 DEBT ISSUANCE COSTS 2 us-gaap_UnamortizedDebtIssuanceExpense us-gaap true debit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 19667000 19667 false false false 2 false true false false 24672000 24672 false false false xbrli:monetaryItemType monetary The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset. No authoritative reference available. false 19 DERIVATIVE ASSETS 2 us-gaap_CommodityContractAssetNoncurrent us-gaap true debit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 8580000 8580 false false false 2 false true false false 8473000 8473 false false false xbrli:monetaryItemType monetary Carrying amount as of the balance sheet date of the asset arising from commodity contracts such as futures contracts tied to the movement of a particular commodity, which are expected to be converted into cash or otherwise disposed of after a year or beyond the normal operating cycle, if longer. No authoritative reference available. false 20 OTHER LONG-TERM ASSETS 2 us-gaap_OtherAssetsNoncurrent us-gaap true debit instant No definition available. false false false false false false false false false false false totallabel false 1 false true false false 22766000 22766 false false false 2 false true false false 22266000 22266 false false false xbrli:monetaryItemType monetary Aggregate carrying amount, as of the balance sheet date, of noncurrent assets not separately disclosed in the balance sheet due to materiality considerations. Noncurrent assets are expected to be realized or consumed after one year (or the normal operating cycle, if longer). Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 17 -Article 5 true 21 TOTAL 2 us-gaap_Assets us-gaap true debit instant No definition available. false false false false false false false false false false false totallabel false 1 false true false false 4172725000 4172725 false false false 2 false true false false 4029542000 4029542 false false false xbrli:monetaryItemType monetary Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Concepts (CON) -Number 6 -Paragraph 25 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 18 -Article 5 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 12 -Article 7 true 23 CURRENT LIABILITIES: 2 us-gaap_LiabilitiesCurrentAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 24 Accounts payable 3 us-gaap_AccountsPayableCurrent us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 13904000 13904 false false false 2 false true false false 14023000 14023 false false false xbrli:monetaryItemType monetary Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 19 -Subparagraph a -Article 5 false 25 Accrued capital expenditures 3 us-gaap_OtherAccruedLiabilitiesCurrent us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 56158000 56158 false false false 2 false true false false 29998000 29998 false false false xbrli:monetaryItemType monetary Carrying value as of the balance sheet date of obligations incurred through that date and payable arising from transactions not otherwise specified in the taxonomy. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 43 -Chapter 3 -Section A -Paragraph 7 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 20 -Article 5 false 26 Accrued liabilities 3 us-gaap_AccruedLiabilitiesCurrent us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 69179000 69179 false false false 2 false true false false 62891000 62891 false false false xbrli:monetaryItemType monetary Carrying value as of the balance sheet date of obligations incurred and payable, pertaining to costs that are statutory in nature, are incurred on contractual obligations, or accumulate over time and for which invoices have not yet been received or will not be rendered. Examples include taxes, interest, rent and utilities. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 20 -Article 5 false 27 Accrued interest 3 us-gaap_InterestPayableCurrent us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 10514000 10514 false false false 2 false true false false 10501000 10501 false false false xbrli:monetaryItemType monetary Carrying value as of the balance sheet date of [accrued] interest payable on all forms of debt, including trade payables, that has been incurred and is unpaid. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 43 -Chapter 3 -Section A -Paragraph 7 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 20 -Article 5 false 28 Oil and gas sales payable 3 us-gaap_OilAndGasSalesPayableCurrent us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 64593000 64593 false false false 2 false true false false 46327000 46327 false false false xbrli:monetaryItemType monetary Carrying value as of the balance sheet date of obligations incurred and payable to third parties for oil and gas that has been sold but not delivered. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 19 -Subparagraph a -Article 5 false 29 Accrued employee compensation and benefits 3 us-gaap_EmployeeRelatedLiabilitiesCurrent us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 18405000 18405 false false false 2 false true false false 22105000 22105 false false false xbrli:monetaryItemType monetary Total of the carrying values as of the balance sheet date of obligations incurred through that date and payable for obligations related to services received from employees, such as accrued salaries and bonuses, payroll taxes and fringe benefits. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 20 -Article 5 false 30 Production taxes payable 3 us-gaap_SalesAndExciseTaxPayableCurrent us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 22473000 22473 false false false 2 false true false false 21188000 21188 false false false xbrli:monetaryItemType monetary Carrying value as of the balance sheet date of liabilities incurred through that date and payable for statutory sales and use taxes, including value added tax. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 19 -Subparagraph a -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 43 -Chapter 3 -Section A -Paragraph 7 false 31 Deferred gain on sale 3 us-gaap_DeferredGainOnSaleOfProperty us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 12776000 12776 false false false 2 false true false false 12966000 12966 false false false xbrli:monetaryItemType monetary Amount of gain on the sale of property that does not qualify for gain recognition as of the balance sheet date. No authoritative reference available. false 32 Derivative liabilities 3 us-gaap_HedgingLiabilitiesCurrent us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 26269000 26269 false false false 2 false true false false 49551000 49551 false false false xbrli:monetaryItemType monetary Carrying amount as of the balance sheet date of the liability arising from a financial instrument or a contract used to mitigate a specified risk (hedge), and which are expected to be converted into cash or otherwise disposed of within a year or the normal operating cycle, if longer. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 17 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Audit and Accounting Guide (AAG) -Number AAG-BRD -Chapter 7 -Paragraph 41 -IssueDate 2006-05-01 false 33 Deferred income taxes 3 us-gaap_DeferredTaxLiabilitiesCurrent us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 5811000 5811 false false false 2 false true false false 11325000 11325 false false false xbrli:monetaryItemType monetary Represents the current portion of deferred tax liabilities, which result from applying the applicable tax rate to net taxable temporary differences pertaining to each jurisdiction to which the entity is obligated to pay income tax. A current taxable temporary difference is a difference between the tax basis and the carrying amount of a current asset or liability in the financial statements prepared in accordance with generally accepted accounting principles. In a classified statement of financial position, an enterprise shall separate deferred tax liabilities and assets into a current amount and a noncurrent amount. Deferred tax liabilities and assets shall be classified as current or noncurrent based on the classification of the related asset or liability for financial reporting. A deferred tax liability or asset that is not related to an asset or liability for financial reporting, including deferred tax assets related to carryforwards, shall be classified according to the expected reversal date of the temporary difference. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 109 -Paragraph 41, 42, 43 false 34 Tax sharing liability 3 wll_TaxSharingLiabilityCurrent wll false credit instant Tax Sharing Liability Current. false false false false false false false false false false false totallabel false 1 false true false false 1857000 1857 false false false 2 false true false false 1857000 1857 false false false xbrli:monetaryItemType monetary Tax Sharing Liability Current. No authoritative reference available. true 35 Total current liabilities 3 us-gaap_LiabilitiesCurrent us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 301939000 301939 false false false 2 false true false false 282732000 282732 false false false xbrli:monetaryItemType monetary Total obligations incurred as part of normal operations that are expected to be paid during the following twelve months or within one business cycle, if longer. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 21 -Article 5 false 36 NON-CURRENT LIABILITIES: 2 us-gaap_LiabilitiesNoncurrentAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 37 Long-term debt 3 us-gaap_LongTermDebtNoncurrent us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 649603000 649603 false false false 2 false true false false 779585000 779585 false false false xbrli:monetaryItemType monetary Sum of the carrying values as of the balance sheet date of all long-term debt, which is debt initially having maturities due after one year from the balance sheet date or beyond the operating cycle, if longer, but excluding the portions thereof scheduled to be repaid within one year (current maturities) or the normal operating cycle, if longer, and after deducting unamortized discount or premiums, if any. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 38 Deferred income taxes 3 us-gaap_DeferredTaxLiabilitiesNoncurrent us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 464343000 464343 false false false 2 false true false false 341037000 341037 false false false xbrli:monetaryItemType monetary Represents the noncurrent portion of deferred tax liabilities, which result from applying the applicable tax rate to net taxable temporary differences pertaining to each jurisdiction to which the entity is obligated to pay income tax. A noncurrent taxable temporary difference is a difference between the tax basis and the carrying amount of a noncurrent asset or liability in the financial statements prepared in accordance with generally accepted accounting principles. In a classified statement of financial position, an enterprise shall separate deferred tax liabilities and assets into a current amount and a noncurrent amount. Deferred tax liabilities and assets shall be classified as current or noncurrent based on the classification of the related asset or liability for financial reporting. A deferred tax liability or asset that is not related to an asset or liability for financial reporting, including deferred tax assets related to carryforwards, shall be classified according to the expected reversal date of the temporary difference. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 109 -Paragraph 41, 42 false 39 Derivative liabilities 3 wll_HedgingLiabilitiesNoncurrent wll false credit instant Hedging Liabilities, Noncurrent. false false false false false false false false false false false verboselabel false 1 false true false false 73750000 73750 false false false 2 false true false false 137621000 137621 false false false xbrli:monetaryItemType monetary Hedging Liabilities, Noncurrent. No authoritative reference available. false 40 Production Participation Plan liability 3 us-gaap_DeferredCompensationLiabilityClassifiedNoncurrent us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 75125000 75125 false false false 2 false true false false 69433000 69433 false false false xbrli:monetaryItemType monetary Aggregate carrying value as of the balance sheet date of the liabilities for all deferred compensation arrangements payable beyond one year (or the operating cycle, if longer). No authoritative reference available. false 41 Asset retirement obligations 3 us-gaap_OilAndGasReclamationLiabilityNoncurrent us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 72216000 72216 false false false 2 false true false false 66846000 66846 false false false xbrli:monetaryItemType monetary Amount of a reclamation liability that is associated with a legal obligation for the closure and reclamation of oil and gas properties. No authoritative reference available. false 42 Deferred gain on sale 3 us-gaap_OtherDeferredCreditsNoncurrent us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 50880000 50880 false false false 2 false true false false 58462000 58462 false false false xbrli:monetaryItemType monetary Carrying amount as of the balance sheet date of unearned revenue or income not otherwise specified in the taxonomy which is expected to be taken into income after one year or beyond the normal operating cycle, if longer. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 13 -Section A false 43 Tax sharing liability 3 wll_TaxSharingLiabilityNonCurrent wll false credit instant Tax Sharing Liability Non Current. false false false false false false false false false false false verboselabel false 1 false true false false 21444000 21444 false false false 2 false true false false 20744000 20744 false false false xbrli:monetaryItemType monetary Tax Sharing Liability Non Current. No authoritative reference available. false 44 Other long-term liabilities 3 us-gaap_OtherLiabilitiesNoncurrent us-gaap true credit instant No definition available. false false false false false false false false false false false totallabel false 1 false true false false 3091000 3091 false false false 2 false true false false 2997000 2997 false false false xbrli:monetaryItemType monetary Aggregate carrying amount, as of the balance sheet date, of noncurrent obligations not separately disclosed in the balance sheet due to materiality considerations. Noncurrent liabilities are expected to be paid after one year (or the normal operating cycle, if longer). Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 24 -Article 5 true 45 Total non-current liabilities 3 us-gaap_LiabilitiesNoncurrent us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 1410452000 1410452 false false false 2 false true false false 1476725000 1476725 false false false xbrli:monetaryItemType monetary Total obligations incurred as part of normal operations that is expected to be repaid beyond the following twelve months or one business cycle. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22, 23, 24, 25, 26, 27 -Article 5 false 46 COMMITMENTS AND CONTINGENCIES 2 us-gaap_CommitmentsAndContingencies2009 us-gaap true na duration No definition available. false false false false false false false false false false false verboselabel false 1 false false false false 0 0     false false false 2 false false false false 0 0     false false false xbrli:stringItemType string Represents the caption on the face of the balance sheet to indicate that the entity has entered into (1) purchase or supply arrangements that will require expending a portion of its resources to meet the terms thereof, and (2) is exposed to potential losses or, less frequently, gains, arising from (a) possible claims against a company's resources due to future performance under contract terms, and (b) possible losses or likely gains from uncertainties that will ultimately be resolved when one or more future events that are deemed likely to occur do occur or fail to occur. This caption alerts the reader that one or more notes to the financial statements disclose pertinent information about the entity's commitments and contingencies. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 19 -Article 7 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 5 -Paragraph 8, 9 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 25 -Article 5 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 17 -Article 9 false 47 STOCKHOLDERS' EQUITY: 2 us-gaap_StockholdersEquityAbstract us-gaap true na duration No definition available. false false false false false true false false false false false label false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 48 Preferred stock, $0.001 par value, 5,000,000 shares authorized; 6.25% convertible perpetual preferred stock, 3,450,000 shares issued and outstanding as of June 30, 2010 and December 31, 2009, aggregate liquidation preference of $345,000,000 3 us-gaap_PreferredStockValue us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 3000 3 false false false 2 false true false false 3000 3 false false false xbrli:monetaryItemType monetary Dollar value of issued nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) whether issued at par value, no par or stated value. This item includes treasury stock repurchased by the entity. Note: elements for number of nonredeemable preferred shares, par value and other disclosure concepts are in another section within stockholders' equity. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 129 -Paragraph 2, 3, 4, 5, 6, 7, 8 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 12 -Paragraph 10 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 29 -Article 5 false 49 Common stock, $0.001 par value, 175,000,000 shares authorized; 51,441,800 issued and 50,998,477 outstanding as of June 30, 2010, 51,363,638 issued and 50,845,374 outstanding as of December 31, 2009 3 us-gaap_CommonStockValue us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 51000 51 false false false 2 false true false false 51000 51 false false false xbrli:monetaryItemType monetary Dollar value of issued common stock whether issued at par value, no par or stated value. This item includes treasury stock repurchased by the entity. Note: elements for number of common shares, par value and other disclosure concepts are in another section within stockholders' equity. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 30 -Article 5 false 50 Additional paid-in capital 3 us-gaap_AdditionalPaidInCapital us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 1545370000 1545370 false false false 2 false true false false 1546635000 1546635 false false false xbrli:monetaryItemType monetary Excess of issue price over par or stated value of the entity's capital stock and amounts received from other transactions involving the entity's stock or stockholders. Includes adjustments to additional paid in capital. Some examples of such adjustments include recording the issuance of debt with a beneficial conversion feature and certain tax consequences of equity instruments awarded to employees. Use this element for the aggregate amount of APIC associated with common AND preferred stock. For APIC associated with only common stock, use the element Additional Paid In Capital, Common Stock. For APIC associated with only preferred stock, use the element Additional Paid In Capital, Preferred Stock. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 31 -Article 5 false 51 Accumulated other comprehensive income 3 us-gaap_AccumulatedOtherComprehensiveIncomeLossCumulativeChangesInNetGainLossFromCashFlowHedgesEffectNetOfTax us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 10780000 10780 false false false 2 false true false false 20413000 20413 false false false xbrli:monetaryItemType monetary Accumulated change, net of tax, in accumulated gains and losses from derivative instruments designated and qualifying as the effective portion of cash flow hedges. Includes an entity's share of an equity investee's increase (decrease) in deferred hedging gains or losses. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 26 false 52 Retained earnings 3 us-gaap_RetainedEarningsAccumulatedDeficit us-gaap true credit instant No definition available. false false false false false false false false false false false totallabel false 1 false true false false 904130000 904130 false false false 2 false true false false 702983000 702983 false false false xbrli:monetaryItemType monetary The cumulative amount of the reporting entity's undistributed earnings or deficit. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 12 -Paragraph 10 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 31 -Article 5 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 true 53 Total stockholders' equity 3 us-gaap_StockholdersEquity us-gaap true credit instant No definition available. false false false false false false false false false false false totallabel false 1 false true false false 2460334000 2460334 false false false 2 false true false false 2270085000 2270085 false false false xbrli:monetaryItemType monetary Total of all Stockholders' Equity (deficit) items, net of receivables from officers, directors owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph A3 -Appendix A Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 4 -Section E Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 29, 30, 31 -Article 5 true 54 TOTAL 2 us-gaap_LiabilitiesAndStockholdersEquity us-gaap true credit instant No definition available. false false false false false false false false false false false totallabel false 1 true true false false 4172725000 4172725 false false false 2 true true false false 4029542000 4029542 false false false xbrli:monetaryItemType monetary Total of all Liabilities and Stockholders' Equity items. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 32 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 25 -Article 7 true 2 49 false Thousands UnKnown UnKnown false true