Income Taxes	3 Months Ended
Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes For the quarter ended December 31, 2017, we recorded an income tax benefit of $13.6 million. For the quarter ended January 1, 2017, we recorded income tax provision of $9.1 million. The difference in our effective tax rate from the U.S. statutory rate primarily reflects the impact of the mix of domestic and international pre-tax income, valuation allowance and credits. The income tax benefit this quarter includes $24.2 million of provisional benefit related to certain aspects of the Tax Cuts and Jobs Act ("TCJA"), as discussed further below, offset by increases in unrecognized tax benefits for uncertain tax positions. The TCJA was enacted on December 22, 2017, and permanently reduces the U.S. federal corporate tax rate from 35% to 21%, requires companies to pay a one-time transition tax on earnings of certain foreign subsidiaries that were previously tax-deferred and creates new taxes on certain foreign sourced earnings. The statutory rate applicable to our fiscal year ending September 30, 2018 will be 24.5%, based on a fiscal year blended rate calculation. Accounting Standard Codification ("ASC") 740 requires filers to record the effect of tax law changes in the period enacted. However, the SEC issued Staff Accounting Bulletin No. 118 ("SAB 118") , that permits filers to record provisional amounts during a measurement period ending no later than one year from the date of the TCJA enactment. As of December 31, 2017, we have not completed our accounting for the tax effects of enactment of the TCJA. However, we have recorded a provisional tax benefit of $12.4 million for the remeasurement of certain deferred tax liabilities in the U.S. from 35% to 21% and a provisional tax benefit of $11.8 million for the recognition of the alternative minimum tax credits that will be fully refundable under the TCJA over the next several years. These provisional amounts are included as components of provision for (benefit from) income taxes as reported in our consolidated statements of operations and comprehensive income. We are still in the process of analyzing the earnings and profits and tax pools of our foreign subsidiaries, particularly with regards to subsidiaries from recent acquisitions, to reasonably estimate the effects of the one-time transition tax and, therefore, have not recorded a provisional impact. The tax expense impact of the one-time transition tax to be determined may be partially or fully offset by a release of valuation allowance for the utilization of existing net operating losses and tax credits that may reduce the amount of related taxes payable. Additionally, we have not recorded provisional amounts for other aspects of the TCJA, including the potential impact of items effective January 1, 2018 and continue to account for those items based on our existing accounting under ASC 740 and the provisions of the tax laws that were in effect immediately prior to enactment. Further, we anticipate the Department of the Treasury, FASB and other regulators to release additional guidance and authority that could affect our accounting for the tax effects of enactment of the TCJA. We file U.S. federal, state, and foreign income tax returns in jurisdictions with varying statutes of limitations. Fiscal years 2007 through 2016 generally remain subject to examination by federal and most state tax authorities and in significant foreign jurisdictions. Each quarter, we reassess our uncertain tax positions for additional unrecognized tax benefits, interest and penalties, and deletions due to statute expirations. Based on federal, state and foreign statute expirations in various jurisdictions, we anticipate a potential decrease in unrecognized tax benefits of approximately $23.3 million within the next twelve months. We establish liabilities for possible assessments by tax authorities resulting from known tax exposures including, but not limited to, international tax issues and certain tax credits. The Internal Revenue Service ("IRS") is currently examining our income tax returns for tax years 2007 through 2014 and the Canada Revenue Agency ("CRA") is currently examining income tax returns for tax years 2007 through 2008 and 2011 through 2015. As of December 31, 2017, the IRS and the CRA have raised questions primarily related to transfer pricing. We believe that our position is appropriate and that an adequate provision has been made for any adjustments that may result from tax examinations. However, the outcome of tax audits cannot be predicted with certainty. If any issues addressed in our tax audits are resolved in a manner not consistent with our expectations, we would be required to adjust our provision for income tax in the period such resolution occurs. While we believe our reported results are appropriate, any significant adjustments could have a material adverse effect on our results of operations, cash flows and financial position if not resolved within our expectations.

Income Taxes

For the quarter ended December 31, 2017, we recorded an income tax benefit of $13.6 million. For the quarter ended January 1, 2017, we recorded income tax provision of $9.1 million. The difference in our effective tax rate from the U.S. statutory rate primarily reflects the impact of the mix of domestic and international pre-tax income, valuation allowance and credits. The income tax benefit this quarter includes $24.2 million of provisional benefit related to certain aspects of the Tax Cuts and Jobs Act ("TCJA"), as discussed further below, offset by increases in unrecognized tax benefits for uncertain tax positions.

The TCJA was enacted on December 22, 2017, and permanently reduces the U.S. federal corporate tax rate from 35% to 21%, requires companies to pay a one-time transition tax on earnings of certain foreign subsidiaries that were previously tax-deferred and creates new taxes on certain foreign sourced earnings. The statutory rate applicable to our fiscal year ending September 30, 2018 will be 24.5%, based on a fiscal year blended rate calculation. Accounting Standard Codification ("ASC") 740 requires filers to record the effect of tax law changes in the period enacted. However, the SEC issued Staff Accounting Bulletin No. 118 ("SAB 118") , that permits filers to record provisional amounts during a measurement period ending no later than one year from the date of the TCJA enactment.

As of December 31, 2017, we have not completed our accounting for the tax effects of enactment of the TCJA. However, we have recorded a provisional tax benefit of $12.4 million for the remeasurement of certain deferred tax liabilities in the U.S. from 35% to 21% and a provisional tax benefit of $11.8 million for the recognition of the alternative minimum tax credits that will be fully refundable under the TCJA over the next several years. These provisional amounts are included as components of provision for (benefit from) income taxes as reported in our consolidated statements of operations and comprehensive income.

We are still in the process of analyzing the earnings and profits and tax pools of our foreign subsidiaries, particularly with regards to subsidiaries from recent acquisitions, to reasonably estimate the effects of the one-time transition tax and, therefore, have not recorded a provisional impact. The tax expense impact of the one-time transition tax to be determined may be partially or fully offset by a release of valuation allowance for the utilization of existing net operating losses and tax credits that may reduce the amount of related taxes payable.

Additionally, we have not recorded provisional amounts for other aspects of the TCJA, including the potential impact of items effective January 1, 2018 and continue to account for those items based on our existing accounting under ASC 740 and the provisions of the tax laws that were in effect immediately prior to enactment. Further, we anticipate the Department of the Treasury, FASB and other regulators to release additional guidance and authority that could affect our accounting for the tax effects of enactment of the TCJA.

We file U.S. federal, state, and foreign income tax returns in jurisdictions with varying statutes of limitations. Fiscal years 2007 through 2016 generally remain subject to examination by federal and most state tax authorities and in significant foreign jurisdictions. Each quarter, we reassess our uncertain tax positions for additional unrecognized tax benefits, interest and penalties, and deletions due to statute expirations. Based on federal, state and foreign statute expirations in various jurisdictions, we anticipate a potential decrease in unrecognized tax benefits of approximately $23.3 million within the next twelve months.

We establish liabilities for possible assessments by tax authorities resulting from known tax exposures including, but not limited to, international tax issues and certain tax credits. The Internal Revenue Service ("IRS") is currently examining our income tax returns for tax years 2007 through 2014 and the Canada Revenue Agency ("CRA") is currently examining income tax returns for tax years 2007 through 2008 and 2011 through 2015. As of December 31, 2017, the IRS and the CRA have raised questions primarily related to transfer pricing. We believe that our position is appropriate and that an adequate provision has been made for any adjustments that may result from tax examinations. However, the outcome of tax audits cannot be predicted with certainty. If any issues addressed in our tax audits are resolved in a manner not consistent with our expectations, we would be required to adjust our provision for income tax in the period such resolution occurs. While we believe our reported results are appropriate, any significant adjustments could have a material adverse effect on our results of operations, cash flows and financial position if not resolved within our expectations.