Income Taxes (Notes)	3 Months Ended
Mar. 31, 2018
Income Taxes [Abstract]
Income Tax Disclosure	Income Taxes Income tax expense during interim periods is based on our estimated annual effective income tax rate plus any discrete items, which are recorded in the period in which they occur. Discrete items include, among others, such events as changes in estimates due to the finalization of tax returns, tax audit settlements, expiration of statutes of limitation, and increases or decreases in valuation allowances on deferred tax assets. Our effective tax rate was an expense of 25.7% and a benefit of 77.4% for the three months ended March 31, 2018 and 2017, respectively. The lower effective tax rate for the three months ended March 31, 2017 was primarily due to the effects of the IRS audit settlement and windfall tax benefits recognized on the settlement of employee share-based awards, partially offset by a higher corporate income tax rate, which was reduced from 35% to 21% as a result of the Tax Cuts and Jobs Act ("the Tax Act") enacted in December 2017. The higher effective tax rate for the three months ended March 31, 2018 was primarily a result of limitation on deductibility of certain executive compensation and repeal of the domestic manufacturing deduction. We continue to assess forthcoming guidance and accounting interpretations on the effects of the Tax Act, which could potentially affect the provisional estimates that were recorded at December 31, 2017, and expect to complete our analysis within the measurement period. Unrecognized Tax Benefits As of March 31, 2018, the total amount of our unrecognized tax benefits was $79.5 million and the total amount of our accrued interest was $11.1 million. In March 2017, we received from the IRS Office of Appeals the fully executed Form 870-AD for the years 1999-2005, which effectively settled the issues under audit for those years. Tax years subsequent to 2005 remain open to review and adjustment by the IRS. In addition, we are under audit by various state jurisdictions for years 2000 through 2016. There are currently no federal or provincial audits in Canada. It is reasonably possible that the amount of unrecognized tax benefits could significantly decrease over the next 12 months as certain tax positions will be released as a result of Statutes closing. However, since the years to which uncertain tax positions relate remain subject to review by the tax authorities, a current estimate of the range of decrease that may occur within the next 12 months cannot be made.

Income Taxes

Income tax expense during interim periods is based on our estimated annual effective income tax rate plus any discrete items, which are recorded in the period in which they occur. Discrete items include, among others, such events as changes in estimates due to the finalization of tax returns, tax audit settlements, expiration of statutes of limitation, and increases or decreases in valuation allowances on deferred tax assets. Our effective tax rate was an expense of 25.7% and a benefit of 77.4% for the three months ended March 31, 2018 and 2017, respectively. The lower effective tax rate for the three months ended March 31, 2017 was primarily due to the effects of the IRS audit settlement and windfall tax benefits recognized on the settlement of employee share-based awards, partially offset by a higher corporate income tax rate, which was reduced from 35% to 21% as a result of the Tax Cuts and Jobs Act ("the Tax Act") enacted in December 2017. The higher effective tax rate for the three months ended March 31, 2018 was primarily a result of limitation on deductibility of certain executive compensation and repeal of the domestic manufacturing deduction. We continue to assess forthcoming guidance and accounting interpretations on the effects of the Tax Act, which could potentially affect the provisional estimates that were recorded at December 31, 2017, and expect to complete our analysis within the measurement period.

Unrecognized Tax Benefits

As of March 31, 2018, the total amount of our unrecognized tax benefits was $79.5 million and the total amount of our accrued interest was $11.1 million.

In March 2017, we received from the IRS Office of Appeals the fully executed Form 870-AD for the years 1999-2005, which effectively settled the issues under audit for those years. Tax years subsequent to 2005 remain open to review and adjustment by the IRS. In addition, we are under audit by various state jurisdictions for years 2000 through 2016. There are currently no federal or provincial audits in Canada. It is reasonably possible that the amount of unrecognized tax benefits could significantly decrease over the next 12 months as certain tax positions will be released as a result of Statutes closing. However, since the years to which uncertain tax positions relate remain subject to review by the tax authorities, a current estimate of the range of decrease that may occur within the next 12 months cannot be made.