Income Taxes	9 Months Ended
Income Taxes	Sep. 30, 2019
Components of Income Tax Expense (Benefit), Continuing Operations [Abstract]
Income Taxes	Income Taxes Valaris plc, our parent company, is domiciled and resident in the U.K. Our subsidiaries conduct operations and earn income in numerous countries and are subject to the laws of taxing jurisdictions within those countries. The income of our non-U.K. subsidiaries is generally not subject to U.K. taxation. Income tax rates imposed in the tax jurisdictions in which our subsidiaries conduct operations vary, as does the tax base to which the rates are applied. In some cases, tax rates may be applicable to gross revenues, statutory or negotiated deemed profits or other bases utilized under local tax laws, rather than to net income. Therefore, we generally incur income tax expense in periods in which we operate at a loss. Our drilling rigs frequently move from one taxing jurisdiction to another to perform contract drilling services. In some instances, the movement of our drilling rigs among taxing jurisdictions will involve the transfer of ownership of the drilling rigs among our subsidiaries. As a result of frequent changes in the taxing jurisdictions in which our drilling rigs are operated and/or owned, changes in the overall level of our income and changes in tax laws, our consolidated effective income tax rate may vary substantially from one reporting period to another. Income tax rates and taxation systems in the jurisdictions in which our subsidiaries conduct operations vary and our subsidiaries are frequently subjected to minimum taxation regimes. In some jurisdictions, tax liabilities are based on gross revenues, statutory or negotiated deemed profits or other factors, rather than on net income and our subsidiaries are frequently unable to realize tax benefits when they operate at a loss. Accordingly, during periods of declining profitability, our consolidated income tax expense generally does not decline proportionally with consolidated income, which results in higher effective income tax rates. Furthermore, we generally continue to incur income tax expense in periods in which we operate at a loss on a consolidated basis. Historically, we calculated our provision for income taxes during interim reporting periods by applying the estimated annual effective tax rate for the full fiscal year to pre-tax income or loss, excluding discrete items, for the reporting period. We determined that since small changes in estimated pre-tax income or loss would result in significant changes in the estimated annual effective tax rate, the historical method would not provide a reliable estimate of income taxes for the three-month and nine-month periods ended September 30, 2019 and 2018. We used a discrete effective tax rate method to calculate income taxes for the three-month and nine-month periods ended September 30, 2019 and 2018. We will continue to evaluate income tax estimates under the historical method in subsequent quarters and employ a discrete effective tax rate method if warranted. Discrete income tax benefit for the three-month period ended September 30, 2019 was $18.4 million and was primarily attributable to restructuring transactions, the impairment of a drilling rig, changes in liabilities for unrecognized tax benefits associated with tax positions taken in prior years and other resolutions of prior year tax matters, partially offset by discrete tax expense resulting from gains on the repurchase of debt. Discrete income tax benefit for the three-month period ended September 30, 2018 was $7.9 million and was primarily attributable to an election under U.S. Treasury Regulations not to apply U.S. 2017 operating losses to deemed repatriated income, which provided for utilization of foreign tax credits that were subject to valuation allowance, and U.S. tax reform, partially offset by discrete tax expense related to the settlement of arbitration proceedings, rig sales and unrecognized tax benefits associated with tax positions taken in prior years. Excluding the aforementioned discrete tax items, income tax expense for the three-month periods ended September 30, 2019 and 2018 was $19.9 million and $31.2 million, respectively. Discrete income tax benefit for the nine-month period ended September 30, 2019 was $19.0 million and was primarily attributable to restructuring transactions, the impairment of a drilling rig, changes in liabilities for unrecognized tax benefits associated with tax positions taken in prior years and other resolutions of prior year tax matters, partially offset by discrete tax expense resulting from gains on the repurchase of debt. Discrete income tax benefit for the nine-month period ended September 30, 2018 was $19.1 million and was primarily attributable to an election under U.S. Treasury Regulations not to apply U.S. 2017 operating losses to deemed repatriated income, which provided for utilization of foreign tax credits that were subject to valuation allowance, U.S. tax reform and a restructuring transaction, partially offset by discrete tax expense related to the settlement of arbitration proceedings, repurchase and redemption of senior notes, unrecognized tax benefits associated with tax positions taken in prior years and rig sales. Excluding the aforementioned discrete tax items, income tax expense for the nine-month periods ended September 30, 2019 and 2018 was $84.6 million and $85.5 million, respectively. Recent Tax Assessments During 2019, the Luxembourg tax authorities issued aggregate tax assessments totaling approximately €142.0 million (approximately $155.0 million converted using the current period-end exchange rates) related to tax years 2014, 2015 and 2016 for several of Rowan’s Luxembourg subsidiaries, which assessments accrue interest at the rate of 7.2% per annum. Although we are vigorously contesting these assessments, we have recorded an estimated liability for uncertain tax positions taken during these years as part of our acquisition accounting for the Rowan Transaction totaling €93.0 million (approximately $101.0 million converted using the current period-end exchange rates), which could change materially as we complete our evaluation of the filing positions. See Note 3 for additional information. Although the outcome of such assessments and related administrative proceedings cannot be predicted with certainty, an unfavorable outcome could result in a material adverse effect on our financial position, operating results and cash flows. During 2019, the Australian tax authorities issued aggregate tax assessments totaling approximately A$101 million (approximately $68 million converted using the current period-end exchange rate) plus interest related to the examination of certain of our tax returns for years 2011 through 2016. During the third quarter of 2019, we made a A$42 million payment (approximately $29 million at then-current exchange rates) to the Australian tax authorities to litigate the assessment, partially mitigating potential interest on any ultimate assessment outcomes. We believe our tax returns are materially correct as filed, and we are vigorously contesting these assessments. Although the outcome of such assessments and related administrative proceedings cannot be predicted with certainty, we do not expect these matters to have a material adverse effect on our financial position, operating results and cash flows. Other Matters During the three-month period ended September 30, 2019, we completed certain restructuring transactions that generated substantial U.S capital gains and losses. At September 30, 2019, we have recognized a deferred tax asset of $988 million associated with the net capital loss arising from these transactions. Based on our current assessment, this deferred tax asset is subject to a full valuation allowance because we more-likely-than-not will be unable to realize a future benefit from it.