Income Taxes (Notes)	9 Months Ended
Income Taxes (Notes)	Jun. 30, 2020
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes On June 1, 2020, the Kansas legislature passed House Bill 2585 which eliminated the assessment of state income taxes on regulated utilities. This legislation will become effective for the Company on October 1, 2020. Due to the change in the Kansas state tax law, we completed a study of the calculations used to estimate the rate at which state deferred taxes will reverse in the future. As a result, we reduced our deferred tax liability by $32.5 million during the fiscal third quarter. We established a $12.1 million regulatory liability for excess deferred taxes that will be returned to Kansas customers. We are currently working with the Kansas Corporation Commission to determine the amortization period for this liability. We recognized $21.0 million as a one-time income tax benefit in our condensed consolidated statement of comprehensive income for the three and nine months ended June 30, 2020. On March 27, 2020, the Coronavirus Aid, Relief, and Economic Security Act (the “CARES Act”) was signed into law. The CARES Act, among other things, includes provisions relating to refundable payroll tax credits, deferment of employer side social security payments, net operating loss carryback periods, alternative minimum tax credit refunds, modifications to the net interest deduction limitations and technical corrections to tax depreciation methods for qualified improvement property. The CARES Act did not have an impact on our condensed consolidated financial statements for the three and nine months ended June 30, 2020.

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.