Income Taxes	3 Months Ended
Mar. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	6. Income Taxes We are a Cayman Islands entity. The Cayman Islands do not impose corporate income taxes. Consequently, we have calculated income taxes based on the laws and tax rates in effect in the countries in which operations are conducted, or in which we and our subsidiaries are considered resident for income tax purposes. We operate in multiple countries under different legal forms. As a result, we are subject to the jurisdiction of numerous domestic and foreign tax authorities, as well as to tax agreements and treaties among these governments. Tax rates vary between jurisdictions, as does the tax base to which the rates are applied. Taxes may be levied based on net profit before taxes or gross revenues or as withholding tax on revenues. Determination of taxable income in any jurisdiction requires the interpretation of the related tax laws and regulations and the use of estimates and assumptions regarding significant future events, such as the amount, timing and character of deductions, permissible revenue recognition methods under the tax law and the sources and character of income and tax credits. Our income tax expense may vary substantially from one period to another as a result of changes in tax laws, regulations, agreements and treaties, foreign currency exchange restrictions, rig movements or our level of operations or profitability in each tax jurisdiction. Furthermore, our income taxes are generally dependent upon the results of our operations and, when we generate significant revenues in jurisdictions where the income tax liability is based on gross revenues or asset values, there is no correlation between our operating results and the income tax expense. Furthermore, in some jurisdictions we do not pay taxes or receive benefits for certain income and expense items, including interest expense, loss on extinguishment of debt and disposal gains or losses. On December 22, 2017, Public Law 115-97, commonly known as the Tax Cuts and Jobs Act of 2017 (the “Act”) was enacted. The Act, among other things, makes significant changes to the U.S. corporate income tax system, including reducing the federal corporate income tax rate from 35% to 21%; changes certain business-related deductions, including modifying the rules regarding limitations on certain deductions for executive compensation, introducing a capital investment deduction in certain circumstances, placing certain limitations on the interest deduction, modifying the rules regarding the usability of certain net operating losses; and transitions U.S. international taxation from a worldwide tax system to a territorial tax system. Our current tax liability and deferred tax assets in relation to the U.S. operations are based on the newly enacted corporate income tax rate. We continue to monitor and evaluate any new guidance in relation to the Act and potential impact on our financial statements. Deferred income tax assets and liabilities are recorded for the expected future tax consequences of events that have been recognized in our financial statements or tax returns. We provide for deferred taxes on temporary differences between the financial statements and tax bases of assets and liabilities using the enacted tax rates which are expected to apply to taxable income when the temporary differences are expected to reverse. Deferred tax assets are also provided for certain loss and tax credit carryforwards. A valuation allowance is established to reduce deferred tax assets when it is more likely than not that some portion or all of the deferred tax asset will not be realized. In certain jurisdictions we are taxed under preferential tax regimes, which may require our compliance with specified requirements to sustain the tax benefits. We believe we are in compliance with the specified requirements and will continue to make all reasonable efforts to comply; however, our ability to meet the requirements of the preferential tax regimes may be affected by changes in laws, our business operations and other factors affecting our company and industry, many of which are beyond our control. Our periodic tax returns are subject to examination by taxing authorities in the jurisdictions in which we operate in accordance with the normal statute of limitations applicable in a particular jurisdiction. These examinations may result in assessments of additional taxes that are resolved with the authorities or through the courts. Resolution of these matters involves uncertainties and there are no assurances as to the outcome. Our tax years 2010 and forward remain open to examination in many of our jurisdictions and we are currently involved in several tax examinations in jurisdictions where we are operating or have previously operated. As information becomes available during the course of these examinations, we may increase or decrease our estimates of tax assessments and accruals.

6. Income Taxes

We are a Cayman Islands entity. The Cayman Islands do not impose corporate income taxes. Consequently, we have calculated income taxes based on the laws and tax rates in effect in the countries in which operations are conducted, or in which we and our subsidiaries are considered resident for income tax purposes. We operate in multiple countries under different legal forms. As a result, we are subject to the jurisdiction of numerous domestic and foreign tax authorities, as well as to tax agreements and treaties among these governments. Tax rates vary between jurisdictions, as does the tax base to which the rates are applied. Taxes may be levied based on net profit before taxes or gross revenues or as withholding tax on revenues. Determination of taxable income in any jurisdiction requires the interpretation of the related tax laws and regulations and the use of estimates and assumptions regarding significant future events, such as the amount, timing and character of deductions, permissible revenue recognition methods under the tax law and the sources and character of income and tax credits. Our income tax expense may vary substantially from one period to another as a result of changes in tax laws, regulations, agreements and treaties, foreign currency exchange restrictions, rig movements or our level of operations or profitability in each tax jurisdiction. Furthermore, our income taxes are generally dependent upon the results of our operations and, when we generate significant revenues in jurisdictions where the income tax liability is based on gross revenues or asset values, there is no correlation between our operating results and the income tax expense. Furthermore, in some jurisdictions we do not pay taxes or receive benefits for certain income and expense items, including interest expense, loss on extinguishment of debt and disposal gains or losses.

On December 22, 2017, Public Law 115-97, commonly known as the Tax Cuts and Jobs Act of 2017 (the “Act”) was enacted. The Act, among other things, makes significant changes to the U.S. corporate income tax system, including reducing the federal corporate income tax rate from 35% to 21%; changes certain business-related deductions, including modifying the rules regarding limitations on certain deductions for executive compensation, introducing a capital investment deduction in certain circumstances, placing certain limitations on the interest deduction, modifying the rules regarding the usability of certain net operating losses; and transitions U.S. international taxation from a worldwide tax system to a territorial tax system. Our current tax liability and deferred tax assets in relation to the U.S. operations are based on the newly enacted corporate income tax rate. We continue to monitor and evaluate any new guidance in relation to the Act and potential impact on our financial statements.

Deferred income tax assets and liabilities are recorded for the expected future tax consequences of events that have been recognized in our financial statements or tax returns. We provide for deferred taxes on temporary differences between the financial statements and tax bases of assets and liabilities using the enacted tax rates which are expected to apply to taxable income when the temporary differences are expected to reverse. Deferred tax assets are also provided for certain loss and tax credit carryforwards. A valuation allowance is established to reduce deferred tax assets when it is more likely than not that some portion or all of the deferred tax asset will not be realized.

In certain jurisdictions we are taxed under preferential tax regimes, which may require our compliance with specified requirements to sustain the tax benefits. We believe we are in compliance with the specified requirements and will continue to make all reasonable efforts to comply; however, our ability to meet the requirements of the preferential tax regimes may be affected by changes in laws, our business operations and other factors affecting our company and industry, many of which are beyond our control.

Our periodic tax returns are subject to examination by taxing authorities in the jurisdictions in which we operate in accordance with the normal statute of limitations applicable in a particular jurisdiction. These examinations may result in assessments of additional taxes that are resolved with the authorities or through the courts. Resolution of these matters involves uncertainties and there are no assurances as to the outcome. Our tax years 2010 and forward remain open to examination in many of our jurisdictions and we are currently involved in several tax examinations in jurisdictions where we are operating or have previously operated. As information becomes available during the course of these examinations, we may increase or decrease our estimates of tax assessments and accruals.