Mortgage Loans	12 Months Ended
Mortgage Loans	Sep. 30, 2021
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Abstract]
Mortgage Loans	MORTGAGE LOANS Mortgage Loans Held for Sale and Related Derivatives Mortgage loans held for sale consist primarily of single-family residential loans collateralized by the underlying property. The Company typically sells the servicing rights for the majority of loans when the loans are sold. Servicing rights retained are typically sold within six months of loan origination. At September 30, 2021, mortgage loans held for sale had an aggregate carrying value of $2.03 billion and an aggregate outstanding principal balance of $1.97 billion. At September 30, 2020, mortgage loans held for sale had an aggregate carrying value of $1.53 billion and an aggregate outstanding principal balance of $1.46 billion. During the years ended September 30, 2021, 2020 and 2019, mortgage loans originated totaled $16.0 billion, $12.2 billion and $8.7 billion, respectively, and mortgage loans sold totaled $15.5 billion, $11.8 billion and $8.4 billion, respectively. The Company had gains on sales of loans and servicing rights of $619.1 million, $437.2 million and $319.4 million during the years ended September 30, 2021, 2020 and 2019, respectively. Net gains on sales of loans and servicing rights are included in revenues in the consolidated statements of operations. During fiscal 2021, approximately 52% of the Company’s mortgage loans were sold directly to Fannie Mae or into securities backed by Ginnie Mae, and 41% were sold to two other major financial entities. To manage the interest rate risk inherent in its mortgage operations, the Company hedges its risk using derivative instruments, generally forward sales of mortgage-backed securities (MBS), which are referred to as “hedging instruments” in the following discussion. The Company does not enter into or hold derivatives for trading or speculative purposes. Newly originated loans that have been closed but not committed to third-party purchasers are hedged to mitigate the risk of changes in their fair value. Hedged loans are committed to third-party purchasers typically within three days after origination. The notional amounts of the hedging instruments used to hedge mortgage loans held for sale may vary in relationship to the underlying loan amounts, depending on the movements in the value of each hedging instrument relative to the value of the underlying mortgage loans. The fair value change related to the hedging instruments generally offsets the fair value change in the mortgage loans held for sale. The net fair value change, which for the years ended September 30, 2021, 2020 and 2019 was not significant, is recognized in revenues in the consolidated statements of operations. At September 30, 2021 and 2020, the Company’s mortgage loans held for sale that were not committed to third-party purchasers totaled $1.3 billion and $1.2 billion, respectively. The Company also uses hedging instruments as part of a program to offer below market interest rate financing to its homebuyers. At September 30, 2021 and 2020, the Company had MBS totaling $834.6 million and $1.1 billion, respectively, that did not yet have interest rate lock commitments (IRLCs) or closed loans created or assigned and recorded an asset of $1.1 million at September 30, 2021 and a liability of $5.3 million at September 30, 2020 for the fair value of such MBS position. Loan Commitments and Related Derivatives The Company is party to IRLCs, which are extended to borrowers who have applied for loan funding and meet defined credit and underwriting criteria. At September 30, 2021 and 2020, the notional amount of IRLCs, which are accounted for as derivative instruments recorded at fair value, totaled $1.5 billion and $1.8 billion, respectively. The Company manages interest rate risk related to its IRLCs through the use of best-efforts whole loan delivery commitments and hedging instruments. These instruments are considered derivatives in an economic hedge and are accounted for at fair value with gains and losses recognized in revenues in the consolidated statements of operations. At September 30, 2021 and 2020, the notional amount of best-efforts whole loan delivery commitments totaled $88.8 million and $84.6 million, respectively, and the notional amount of hedging instruments related to IRLCs not yet committed to purchasers totaled $1.4 billion and $1.6 billion, respectively. Other Mortgage Loans and Loss Reserves Mortgage loans are sold with limited recourse provisions derived from industry-standard representations and warranties in the relevant agreements. These representations and warranties primarily involve the absence of misrepresentations by the borrower or other parties, the appropriate underwriting of the loan and in some cases, a required minimum number of payments to be made by the borrower. The Company generally does not retain any other continuing interest related to mortgage loans sold in the secondary market. The majority of other mortgage loans consists of loans repurchased due to these limited recourse obligations. Typically, these loans are impaired, and some result in real estate owned through the foreclosure process. At September 30, 2021 and 2020, the Company’s total other mortgage loans and real estate owned, before loss reserves, totaled $15.0 million and $14.9 million, respectively. The Company has recorded reserves for estimated losses on other mortgage loans, real estate owned and future loan repurchase obligations due to the limited recourse provisions, all of which are recorded as reductions of revenue. The loss reserve for loan repurchase and settlement obligations is estimated based on historical experience, analysis of the volume of mortgages originated, discussions with mortgage purchasers and current housing and credit market conditions, as well as known and projected mortgage loan repurchase requests. The reserve balances at September 30, 2021 and 2020 totaled $5.1 million and $8.9 million, respectively. Other mortgage loans and real estate owned net of the related loss reserves are included in other assets, while loan repurchase obligations are included in accrued expenses and other liabilities in the Company’s consolidated balance sheets.