Income Taxes	3 Months Ended
Dec. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Effective Tax Rate The effective income tax rate was (7.7)% and (6.5)% during the quarters ended December 31, 2018 and 2017, respectively. The provision for income taxes during interim quarterly reporting periods is based on our estimates of the effective tax rates for the full fiscal year. The effective tax rate in any quarter can also be affected positively or negatively by adjustments that are required to be reported in the specific quarter of resolution. The effective tax rate for the three months ended December 31, 2018 and 2017 was both impacted by recording of excess tax benefits relating to stock awards that vested in December of both years. In addition, the quarter ended December 31, 2017 was affected by recording the impact of the Tax Cuts and Jobs Act (the “Tax Act”), enacted on December 22, 2017 by the U.S. government. The Tax Act makes broad and complex changes to the U.S. tax code that affect our fiscal year ended September 30, 2018 and fiscal year ended September 30, 2019, including, but not limited to: (1) reducing the U.S. federal corporate tax rate; (2) requiring a one-time transition tax on certain un-repatriated earnings of foreign subsidiaries; (3) repealing the performance-based compensation exception for certain employees; (4) instituting the concept of Global Intangible Low-Taxed Income (“GILTI”); and (5) instituting the concept of Foreign Derived Intangible Income. The SEC staff issued Staff Accounting Bulletin No. 118 (“SAB 118”) in December 2017, which provides a measurement period that should not extend beyond one year from the Tax Act enactment date for companies to complete the accounting under FASB Accounting Standards Codification (“ASC”) 740, “Accounting for Income Taxes” (“ASC 740”). Information regarding our adoption and prospective impacts of the Tax Act is included in our Annual Report on Form 10-K for our fiscal year ended September 30, 2018. We have completed our analysis consistent with the guidance provided in SAB 118 related to the tax effects of the transition tax and the excessive employee remuneration, which resulted in no additional charges recorded during the quarter ended December 31, 2018. The Tax Act subjects U.S. corporations to tax on their GILTI. Due to the complexity of the new GILTI tax rules, we are continuing to evaluate this provision of the Tax Act and the application of GAAP. Under GAAP, we can make an accounting policy election to either treat taxes due on the GILTI inclusion as a current period expense or factor such amounts into our measurement of deferred taxes. We have not yet adopted an accounting policy in regard to GILTI. The total unrecognized tax benefit for uncertain tax positions is estimated to be $6.5 million and $6.1 million at December 31, 2018 and September 30, 2018, respectively. We recognize interest expense related to unrecognized tax benefits and penalties as part of the provision for income taxes in our condensed consolidated statements of income and comprehensive income. We have accrued interest of $0.4 million and $0.3 million related to unrecognized tax benefits as of December 31, 2018 and September 30, 2018, respectively.

Income Taxes

Effective Tax Rate

The effective income tax rate was (7.7)% and (6.5)% during the quarters ended December 31, 2018 and 2017, respectively. The provision for income taxes during interim quarterly reporting periods is based on our estimates of the effective tax rates for the full fiscal year. The effective tax rate in any quarter can also be affected positively or negatively by adjustments that are required to be reported in the specific quarter of resolution.

The effective tax rate for the three months ended December 31, 2018 and 2017 was both impacted by recording of excess tax benefits relating to stock awards that vested in December of both years. In addition, the quarter ended December 31, 2017 was affected by recording the impact of the Tax Cuts and Jobs Act (the “Tax Act”), enacted on December 22, 2017 by the U.S. government. The Tax Act makes broad and complex changes to the U.S. tax code that affect our fiscal year ended September 30, 2018 and fiscal year ended September 30, 2019, including, but not limited to: (1) reducing the U.S. federal corporate tax rate; (2) requiring a one-time transition tax on certain un-repatriated earnings of foreign subsidiaries; (3) repealing the performance-based compensation exception for certain employees; (4) instituting the concept of Global Intangible Low-Taxed Income (“GILTI”); and (5) instituting the concept of Foreign Derived Intangible Income.

The SEC staff issued Staff Accounting Bulletin No. 118 (“SAB 118”) in December 2017, which provides a measurement period that should not extend beyond one year from the Tax Act enactment date for companies to complete the accounting under FASB Accounting Standards Codification (“ASC”) 740, “Accounting for Income Taxes” (“ASC 740”). Information regarding our adoption and prospective impacts of the Tax Act is included in our Annual Report on Form 10-K for our fiscal year ended September 30, 2018. We have completed our analysis consistent with the guidance provided in SAB 118 related to the tax effects of the transition tax and the excessive employee remuneration, which resulted in no additional charges recorded during the quarter ended December 31, 2018.

The Tax Act subjects U.S. corporations to tax on their GILTI. Due to the complexity of the new GILTI tax rules, we are continuing to evaluate this provision of the Tax Act and the application of GAAP. Under GAAP, we can make an accounting policy election to either treat taxes due on the GILTI inclusion as a current period expense or factor such amounts into our measurement of deferred taxes. We have not yet adopted an accounting policy in regard to GILTI.

The total unrecognized tax benefit for uncertain tax positions is estimated to be $6.5 million and $6.1 million at December 31, 2018 and September 30, 2018, respectively. We recognize interest expense related to unrecognized tax benefits and penalties as part of the provision for income taxes in our condensed consolidated statements of income and comprehensive income. We have accrued interest of $0.4 million and $0.3 million related to unrecognized tax benefits as of December 31, 2018 and September 30, 2018, respectively.