Income Taxes	3 Months Ended
Mar. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	INCOME TAXES Accounting standards state that companies account for income taxes using the asset and liability approach, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of temporary differences between the carrying amounts and the tax basis of assets and liabilities. This method also requires the recognition of future tax benefits, such as net operating loss carryforwards and other tax credits. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to reverse. Valuation allowances are recorded as necessary to reduce deferred tax assets to the amount thereof that is more likely than not to be realized. The likelihood of realizing deferred tax assets is evaluated by, among other things, estimating future taxable income, considering the future reversal of existing deferred tax liabilities to which the deferred tax assets may be applied and assessing the impact of tax planning strategies. For interim periods, accounting standards require that income tax expense be determined by applying the estimated annual effective income tax rate to year-to-date results unless this method does not result in a reliable estimate of year-to-date income tax expense. Each period, the income tax accrual is adjusted to the latest estimate and the difference from the previously accrued year-to-date balance is adjusted to the current quarter. Changes in the profitability estimates in various jurisdictions will impact our quarterly effective income tax rates. For the first three months of 2018, the primary differences between the U.S. statutory rate of 21% and the effective rate applicable to our income relate to state income tax, foreign tax rates and tax deductions related to stock-based compensation. For the first three months of 2017, the primary differences between the U.S. statutory rate of 35% and the effective rate applicable to our continuing operations relate to foreign tax rates, changes in Canadian valuation allowances, and recognition of research and development tax credits from prior years. We periodically review the need for valuation allowances against deferred tax assets and recognize these deferred tax assets to the extent that the realization is more likely than not. As part of our review, we consider all positive and negative evidence, including earnings history, the future reversal of deferred tax liabilities, and the relevant expirations of carryforwards. We believe that the valuation allowances provided are appropriate. If in future periods our earnings estimates differ from the estimates used to establish these valuation allowances, or other objective positive or negative evidence arises, we may be required to record an adjustment resulting in an impact on tax expense (benefit) for that period.

INCOME TAXES

Accounting standards state that companies account for income taxes using the asset and liability approach, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of temporary differences between the carrying amounts and the tax basis of assets and liabilities. This method also requires the recognition of future tax benefits, such as net operating loss carryforwards and other tax credits. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to reverse. Valuation allowances are recorded as necessary to reduce deferred tax assets to the amount thereof that is more likely than not to be realized. The likelihood of realizing deferred tax assets is evaluated by, among other things, estimating future taxable income, considering the future reversal of existing deferred tax liabilities to which the deferred tax assets may be applied and assessing the impact of tax planning strategies.

For interim periods, accounting standards require that income tax expense be determined by applying the estimated annual effective income tax rate to year-to-date results unless this method does not result in a reliable estimate of year-to-date income tax expense.

Each period, the income tax accrual is adjusted to the latest estimate and the difference from the previously accrued year-to-date balance is adjusted to the current quarter. Changes in the profitability estimates in various jurisdictions will impact our quarterly effective income tax rates.

For the first three months of 2018, the primary differences between the U.S. statutory rate of 21% and the effective rate applicable to our income relate to state income tax, foreign tax rates and tax deductions related to stock-based compensation. For the first three months of 2017, the primary differences between the U.S. statutory rate of 35% and the effective rate applicable to our continuing operations relate to foreign tax rates, changes in Canadian valuation allowances, and recognition of research and development tax credits from prior years.

We periodically review the need for valuation allowances against deferred tax assets and recognize these deferred tax assets to the extent that the realization is more likely than not. As part of our review, we consider all positive and negative evidence, including earnings history, the future reversal of deferred tax liabilities, and the relevant expirations of carryforwards. We believe that the valuation allowances provided are appropriate. If in future periods our earnings estimates differ from the estimates used to establish these valuation allowances, or other objective positive or negative evidence arises, we may be required to record an adjustment resulting in an impact on tax expense (benefit) for that period.