Income Taxes	3 Months Ended
Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Income Tax Provision. Our income tax provision for quarterly interim periods is based on an estimated annual effective income tax rate calculated separately from the effect of significant, infrequent or unusual items. Our total income tax provision, including discontinued operations, was a tax expense of $108.0 million for the three months ended December 31, 2017, compared to an income tax benefit of $2.6 million for the three months ended December 31, 2016. Our current fiscal year income tax expense was primarily driven by (1) the remeasurement of our deferred tax assets as a result of the enactment of the Tax Cuts and Jobs Act (Tax Act) during the quarter; and (2) several discrete tax expenses, including the impacts to our stock-based compensation expense as a result of current period activity; both partially offset by (3) the loss incurred from continuing operations. The tax benefit for the three months ended December 31, 2016 was primarily driven by our loss from continuing operations and the Company's completion of work necessary to claim an additional $1.2 million in tax credits, which were recorded in our fiscal 2017 but related to our fiscal 2016. Deferred Tax Assets and Liabilities. The Tax Act is comprehensive tax reform legislation that was enacted by the U.S. government on December 22, 2017. The Tax Act includes significant changes to the Internal Revenue Code, including a reduction in the corporate tax rate from 35% to 21%. Additionally, the Tax Act establishes new laws that will impact our fiscal 2019, including, but not limited to, eliminating the corporate alternative minimum tax (AMT), changes to how existing AMT credits can be realized, and imposing new limitations on the deductibility of certain executive compensation. In connection with our initial analysis of the Tax Act's impacts, and in accordance with the guidance in SAB 118, we recorded a discrete net tax expense of $112.6 million in the period ending December 31, 2017. This net expense is primarily related to the corporate tax rate reduction and the associated remeasurement of our deferred tax assets. While we have recorded a provisional tax expense of $112.6 million based on reasonable estimates of the impact for the reduction in the corporate tax rate, our estimate may be affected by additional analyses related to the Tax Act and temporary differences that will reverse during our fiscal 2018 and subsequent tax years. The Company continues to evaluate its deferred tax assets each period to determine if a valuation allowance is required based on whether it is more likely than not that some portion of these deferred tax assets will not be realized. As of September 30, 2017 and again as of December 31, 2017, we concluded that it is more likely than not that a substantial portion of our deferred tax assets will be realized. As part of our analysis, we considered both the positive and negative factors that impact our profitability, and whether those factors would lead to a change in the estimate of our deferred tax assets that may be realized in the future. Although the Tax Act may result in changes to our taxable income in the future, we do not anticipate these changes would be significant enough to result in a change in our estimate when taken into account with all our factors. As of December 31, 2017, our conclusions on the valuation allowance and Internal Revenue Code Section 382 limitations related to our deferred tax assets remain consistent with the determinations we made during the period ended September 30, 2017, and are based on similar company specific and industry factors to those discussed in Note 13 to the audited consolidated financial statements within our 2017 Annual Report.

Income Taxes

Income Tax Provision. Our income tax provision for quarterly interim periods is based on an estimated annual effective income tax rate calculated separately from the effect of significant, infrequent or unusual items. Our total income tax provision, including discontinued operations, was a tax expense of $108.0 million for the three months ended December 31, 2017, compared to an income tax benefit of $2.6 million for the three months ended December 31, 2016. Our current fiscal year income tax expense was primarily driven by (1) the remeasurement of our deferred tax assets as a result of the enactment of the Tax Cuts and Jobs Act (Tax Act) during the quarter; and (2) several discrete tax expenses, including the impacts to our stock-based compensation expense as a result of current period activity; both partially offset by (3) the loss incurred from continuing operations. The tax benefit for the three months ended December 31, 2016 was primarily driven by our loss from continuing operations and the Company's completion of work necessary to claim an additional $1.2 million in tax credits, which were recorded in our fiscal 2017 but related to our fiscal 2016.

Deferred Tax Assets and Liabilities. The Tax Act is comprehensive tax reform legislation that was enacted by the U.S. government on December 22, 2017. The Tax Act includes significant changes to the Internal Revenue Code, including a reduction in the corporate tax rate from 35% to 21%. Additionally, the Tax Act establishes new laws that will impact our fiscal 2019, including, but not limited to, eliminating the corporate alternative minimum tax (AMT), changes to how existing AMT credits can be realized, and imposing new limitations on the deductibility of certain executive compensation.

In connection with our initial analysis of the Tax Act's impacts, and in accordance with the guidance in SAB 118, we recorded a discrete net tax expense of $112.6 million in the period ending December 31, 2017. This net expense is primarily related to the corporate tax rate reduction and the associated remeasurement of our deferred tax assets. While we have recorded a provisional tax expense of $112.6 million based on reasonable estimates of the impact for the reduction in the corporate tax rate, our estimate may be affected by additional analyses related to the Tax Act and temporary differences that will reverse during our fiscal 2018 and subsequent tax years.

The Company continues to evaluate its deferred tax assets each period to determine if a valuation allowance is required based on whether it is more likely than not that some portion of these deferred tax assets will not be realized. As of September 30, 2017 and again as of December 31, 2017, we concluded that it is more likely than not that a substantial portion of our deferred tax assets will be realized. As part of our analysis, we considered both the positive and negative factors that impact our profitability, and whether those factors would lead to a change in the estimate of our deferred tax assets that may be realized in the future. Although the Tax Act may result in changes to our taxable income in the future, we do not anticipate these changes would be significant enough to result in a change in our estimate when taken into account with all our factors. As of December 31, 2017, our conclusions on the valuation allowance and Internal Revenue Code Section 382 limitations related to our deferred tax assets remain consistent with the determinations we made during the period ended September 30, 2017, and are based on similar company specific and industry factors to those discussed in Note 13 to the audited consolidated financial statements within our 2017 Annual Report.