Income Taxes	3 Months Ended
Income Taxes	Mar. 31, 2020
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 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 profitability levels and changes in tax laws, our annual 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 income tax expense may not decline proportionally with income, which could result in higher effective income tax rates. Furthermore, we will continue to incur income tax expense in periods in which we operate at a loss. 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 periods ended March 31, 2020 and 2019. We used a discrete effective tax rate method to calculate income taxes for the three-month periods ended March 31, 2020 and 2019. 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 March 31, 2020 was $164.4 million and was primarily attributable to a restructuring transaction, implementation of the U.S. Cares Act, changes in liabilities for unrecognized tax benefits associated with tax positions taken in prior years and other resolutions of prior year tax matters. Discrete income tax expense for the three-month period ended March 31, 2019 was $0.6 million and was attributable to 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 March 31, 2020 and 2019 was $12.4 million and $30.9 million, respectively. Restructuring Transactions As discussed in "Note 10 - Debt", on February 3, 2020, Rowan and RCI transferred substantially all their assets and liabilities to Valaris plc and Valaris plc became the obligor on the Rowan Notes. We recognized a tax benefit of $66.0 million during the three-month period ended March 31, 2020 in connection with this transaction. Unrecognized tax benefits During 2019, the Luxembourg tax authorities issued aggregate tax assessments totaling approximately €142.0 million (approximately $156.7 million converted using the current period-end exchange rates) related to tax years 2014, 2015 and 2016 for several of Rowan's Luxembourg subsidiaries. We recorded €93.0 million (approximately $102.6 million converted using the current period-end exchange rates) in purchase accounting related to these assessments. During the first quarter of 2020, in connection with the administrative appeals process, the tax authority withdrew assessments of €142.0 million (approximately $156.7 million converted using the current period-end exchange rates), accepting the associated tax returns as previously filed. Accordingly, we de-recognized previously accrued liabilities for uncertain tax positions and net wealth taxes of €79.0 million (approximately $87.2 million converted using the current period-end exchange rates) and €2.0 million (approximately $2.2 million converted using the current period-end exchange rates), respectively. The de-recognition of amounts related to these assessments was recognized as a tax benefit during the three-month period ended March 31, 2020 and is included in changes in operating assets and liabilities on the condensed consolidated statement of cash flows for the three-month period ended March 31, 2020. During 2019, the Australian tax authorities issued aggregate tax assessments totaling approximately A$101 million (approximately $62.0 million converted at current period-end exchange rates) plus interest related to the examination of certain of our tax returns for the 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. We have recorded a $13.6 million liability for these assessments as of March 31, 2020. 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.