Washington Federal (WAFD) 10-Q 2 May 18 2018 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Mar. 31, 2018	Apr. 30, 2018
Document and Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q2
Entity Registrant Name	WASHINGTON FEDERAL INC
Entity Central Index Key	936,528
Current Fiscal Year End Date	--09-30
Entity Filer Category	Large Accelerated Filer
Entity Common Stock Outstanding		84,474,615

CONSOLIDATED STATEMENTS OF FINA

CONSOLIDATED STATEMENTS OF FINANCIAL CONDITION - USD ($) $ in Thousands	Mar. 31, 2018	Sep. 30, 2017
ASSETS
Cash and cash equivalents	$ 256,808	$ 313,070
Available-for-sale securities, at fair value	1,269,271	1,266,209
Held-to-maturity securities, at amortized cost	1,716,566	1,646,856
Loans receivable, net of allowance for loan losses of $127,576 and $123,073	11,224,088	10,882,622
Interest receivable	43,931	41,643
Premises and equipment, net	265,388	263,694
Real estate owned	15,904	20,658
FHLB and FRB stock	126,990	122,990
Bank owned life insurance	213,274	211,330
Intangible assets, including goodwill of $301,368 and $293,153	312,303	298,682
Federal and state income tax assets, net	1,414	0
Other assets	187,193	185,826
Assets	15,633,130	15,253,580
Customer accounts
Transaction deposit accounts	6,463,301	6,361,158
Time deposit accounts	4,675,555	4,473,850
Customer accounts	11,138,856	10,835,008
FHLB advances	2,325,000	2,225,000
Advance payments by borrowers for taxes and insurance	41,285	56,631
Accrued expenses and other liabilities	139,316	131,253
Liabilities	13,644,457	13,247,892
Stockholders’ equity
Common stock, $1.00 par value, 300,000,000 shares authorized; 135,334,158 and 134,957,511 shares issued; 84,749,203 and 87,193,362 shares outstanding	135,334	134,958
Additional paid-in capital	1,664,275	1,660,885
Accumulated other comprehensive income (loss), net of taxes	8,899	5,015
Treasury stock, at cost; 50,584,955 and 47,764,149 shares	(935,039)	(838,060)
Retained earnings	1,115,204	1,042,890
Stockholders' equity attributable to parent	1,988,673	2,005,688
Liabilities and equity	$ 15,633,130	$ 15,253,580

CONSOLIDATED STATEMENTS OF FIN3

CONSOLIDATED STATEMENTS OF FINANCIAL CONDITION (Parentheticals) - USD ($) $ in Thousands	Mar. 31, 2018	Sep. 30, 2017
Statement of Financial Position [Abstract]
Allowance for loan losses	$ 127,576	$ 123,073
Goodwill	$ 301,368	$ 293,153
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, shares authorized (in shares)	300,000,000	300,000,000
Common stock, shares issued (in shares)	135,334,158	134,957,511
Common stock, shares outstanding (in shares)	84,749,203	87,193,362
Treasury stock, shares (in shares)	50,584,955	47,764,149

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
INTEREST INCOME
Loans receivable	$ 126,529	$ 116,034	$ 251,040	$ 230,869
Mortgage-backed securities	17,667	16,226	34,566	29,015
Investment securities and cash equivalents	4,883	3,938	9,253	9,078
Interest income	149,079	136,198	294,859	268,962
INTEREST EXPENSE
Customer accounts	16,414	12,392	31,052	25,409
FHLB advances	15,364	16,079	30,771	32,674
Interest expense	31,778	28,471	61,823	58,083
Net interest income	117,301	107,727	233,036	210,879
Provision (release) for loan losses	(950)	(1,600)	(950)	(1,600)
Net interest income after provision (release) for loan losses	118,251	109,327	233,986	212,479
OTHER INCOME
Gain on sale of investment securities	0	0	0	968
FDIC loss share valuation adjustments	0	0	(8,550)	0
Loan fee income	780	1,087	1,815	2,421
Deposit fee income	6,403	4,904	13,089	10,089
Other income	5,404	4,145	13,028	8,554
Other income, total	12,587	10,136	19,382	22,032
OTHER EXPENSE
Compensation and benefits	31,625	28,833	61,244	55,827
Occupancy	9,013	9,091	17,684	17,541
FDIC insurance premiums	2,852	2,910	5,672	5,749
Product delivery	3,665	3,489	7,621	6,850
Information technology	8,781	6,686	16,710	13,137
Other expense	9,851	6,458	18,797	12,704
Other expense, total	65,787	57,467	127,728	111,808
Gain (loss) on real estate owned, net	(278)	795	(232)	1,193
Income before income taxes	64,773	62,791	125,408	123,896
Income tax expense	15,502	20,721	24,467	40,580
NET INCOME	$ 49,271	$ 42,070	$ 100,941	$ 83,316
PER SHARE DATA
Basic earnings per share (in dollars per share)	$ 0.58	$ 0.47	$ 1.17	$ 0.93
Diluted earnings per share (in dollars per share)	0.57	0.47	1.17	0.93
Dividends paid on common stock per share (in dollars per share)	$ 0.17	$ 0.4	$ 0.32	$ 0.54
Basic weighted average number of shares outstanding (in shares)	85,647,494	89,382,416	86,299,885	89,346,294
Diluted weighted average number of shares outstanding (in shares)	85,747,167	89,736,320	86,422,077	89,732,042

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 49,271	$ 42,070	$ 100,941	$ 83,316
Other comprehensive income (loss) net of tax:
Net unrealized gain (loss) on available-for-sale investment securities	(11,467)	5,685	(13,431)	(11,394)
Reclassification adjustment of net gain (loss) from sale of available-for-sale securities included in net income	0	0	0	968
Related tax benefit (expense)	3,681	(2,089)	4,403	3,832
Other comprehensive income (loss) for available for sale securities, net of tax	(7,786)	3,596	(9,028)	(6,594)
Net unrealized gain (loss) on cash flow hedges of borrowings	10,332	2,395	17,022	31,666
Related tax benefit (expense)	(1,651)	(880)	(4,110)	(11,637)
Other comprehensive income (loss) on long term borrowing hedge, net of tax	8,681	1,515	12,912	20,029
Other comprehensive income (loss) net of tax	895	5,111	2,112	13,435
Other comprehensive income (loss), including cumulative effect adjustment, net of tax			3,884
Comprehensive income	$ 50,166	$ 47,181	$ 104,825	$ 96,751

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Balance, beginning of period at Sep. 30, 2016	$ 1,975,731	$ 134,308	$ 1,648,388	$ 943,877	$ (11,156)	$ (739,686)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	83,316			83,316
Other comprehensive income (loss)	13,435				13,435
Dividends on common stock	(47,995)			(47,995)
Proceeds from exercise of common stock options	6,505	282	6,223
Restricted stock expense	4,171	110	4,061
Exercise of stock warrants	0	124	(124)
Treasury stock acquired	(20,401)					(20,401)
Balance, end of period at Mar. 31, 2017	2,014,762	134,824	1,658,548	979,198	2,279	(760,087)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adjustment pursuant to adoption of ASU 2018-02	0			(1,772)	1,772
Balance, beginning of period at Sep. 30, 2017	2,005,688	134,958	1,660,885	1,042,890	5,015	(838,060)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	100,941			100,941
Other comprehensive income (loss)	2,112				2,112
Dividends on common stock	(26,855)			(26,855)
Proceeds from exercise of common stock options	1,232	56	1,176
Restricted stock expense	2,534	211	2,323
Exercise of stock warrants	0	109	(109)
Treasury stock acquired	(96,979)					(96,979)
Balance, end of period at Mar. 31, 2018	$ 1,988,673	$ 135,334	$ 1,664,275	$ 1,115,204	$ 8,899	$ (935,039)

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 100,941,000	$ 83,316,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization, and accretion expense, net	26,756,000	18,770,000
Cash received from (paid to) FDIC under loss share agreements, net	1,595,000	264,000
Stock based compensation expense	2,534,000	4,171,000
Provision (release) for loan losses	(950,000)	(1,600,000)
Loss (gain) on sale of investment securities	0	(968,000)
Decrease (increase) in accrued interest receivable	(2,288,000)	(2,904,000)
Decrease (increase) in federal and state income tax receivable	(1,414,000)	16,047,000
Decrease (increase) in cash surrender value of bank owned life insurance	(3,012,000)	(3,332,000)
Gain on bank owned life insurance	(2,416,000)	(649,000)
Net realized (gain) loss on sales of premises, equipment, and real estate owned	(1,022,000)	(2,587,000)
Decrease (increase) in other assets	(8,797,000)	15,275,000
Increase (decrease) in accrued expenses and other liabilities	8,277,000	(41,839,000)
Net cash provided by (used in) operating activities	120,204,000	83,964,000
CASH FLOWS FROM INVESTING ACTIVITIES
Origination of loans and principal repayments, net	(199,526,000)	(477,029,000)
Loans purchased	(143,605,000)	(72,856,000)
FHLB & FRB stock purchased	(259,400,000)	(17,209,000)
FHLB & FRB stock redeemed	255,400,000	14,424,000
Available-for-sale securities purchased	(123,324,000)	0
Principal payments and maturities of available-for-sale securities	104,733,000	169,937,000
Proceeds from sales of available-for-sale securities	0	350,890,000
Held-to-maturity securities purchased	(170,836,000)	(415,729,000)
Principal payments and maturities of held-to-maturity securities	98,781,000	131,556,000
Proceeds from sales of real estate owned	6,803,000	10,222,000
Proceeds from settlement of bank owned life insurance	3,484,000	1,231,000
Cash paid for acquisitions	(2,211,000)	0
Proceeds from sales of premises and equipment	1,000	3,956,000
Premises and equipment purchased and REO improvements	(12,819,000)	(4,872,000)
Net cash provided by (used in) investing activities	(442,519,000)	(305,479,000)
CASH FLOWS FROM FINANCING ACTIVITIES
Net increase (decrease) in customer accounts	304,001,000	30,107,000
Proceeds from borrowings	6,485,000,000	430,000,000
Repayments of borrowings	(6,385,000,000)	(360,000,000)
Proceeds from exercise of common stock options and related tax benefit	1,232,000	6,505,000
Dividends paid on common stock	(26,855,000)	(47,995,000)
Treasury stock purchased	(96,979,000)	(20,401,000)
Increase (decrease) in borrower advances related to taxes and insurance, net	(15,346,000)	(672,000)
Net cash provided by (used in) financing activities	266,053,000	37,544,000
Increase (decrease) in cash and cash equivalents	(56,262,000)	(183,971,000)
Cash and cash equivalents at beginning of period	313,070,000	450,368,000
Cash and cash equivalents at end of period	256,808,000	266,397,000
Non-cash investing activities
Real estate acquired through foreclosure	1,329,000	2,134,000
Non-cash financing activities
Stock issued upon exercise of warrants	3,761,000	4,036,000
Cash paid during the period for
Interest	60,870,000	55,599,000
Income taxes	$ 25,265,000	$ 16,903,000

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Nature of Operations - Washington Federal, Inc. (the "Company") is a Washington corporation headquartered in Seattle, Washington. The Company is a bank holding company that conducts its operations through its national bank subsidiary, Washington Federal, National Association (the "Bank"). The Bank is principally engaged in the business of attracting deposits from businesses and the general public and investing these funds, together with borrowings and other funds, in one-to-four family residential mortgage and construction loans, home equity loans, lines of credit, commercial real estate loans, commercial and industrial loans, multi-family and other forms of real estate loans. As used throughout this document, the terms "Washington Federal" or the "Company" refer to Washington Federal, Inc. and its consolidated subsidiaries and the term "Bank" refers to the operating subsidiary Washington Federal, National Association. Basis of Presentation - The Company has prepared the consolidated unaudited interim financial statements included in this report. All intercompany transactions and accounts have been eliminated in consolidation. The preparation of financial statements, in conformity with accounting principles generally accepted in the United States of America (“GAAP”), requires management to make estimates and assumptions that affect amounts reported in the financial statements. Actual results could differ from these estimates. In the opinion of management, all adjustments (consisting only of normal recurring adjustments) necessary for a fair presentation are reflected in the interim financial statements. Certain amounts in the financial statements from prior periods have been reclassified to conform to the current financial statement presentation. The information included in this Form 10-Q should be read in conjunction with the financial statements and related notes in the Company's 2017 Annual Report on Form 10-K (“ 2017 Annual Financial Statements”). Interim results are not necessarily indicative of results for a full year. During the six months ended March 31, 2018 , an immaterial correction was recorded related to acquisitions of insurance agency businesses in prior years. The balance sheet classification correction resulted in an increase in goodwill of $7,135,000 and finite-lived intangible assets of $5,106,000 and a corresponding decrease in other assets of $12,241,000 . Summary of Significant Accounting Policies - The significant accounting policies used in preparation of the Company's consolidated financial statements are disclosed in its 2017 Annual Financial Statements. There have not been any material changes in our significant accounting policies compared to those contained in our 2017 Annual Financial Statements for the year ended September 30, 2017 . Off-Balance-Sheet Credit Exposures - The only material off-balance-sheet credit exposures are loans in process and unused lines of credit, which had a combined balance of $2,157,589,000 and $1,992,905,000 at March 31, 2018 and September 30, 2017 , respectively. The Company estimates losses on off-balance-sheet credit exposures by allocating a loss percentage derived from historical loss factors for each asset class.

New Accounting Pronouncements

New Accounting Pronouncements	6 Months Ended
	Mar. 31, 2018
Accounting Changes and Error Corrections [Abstract]
New Accounting Pronouncements	New Accounting Pronouncements In February 2018, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income . The ASU was issued to address certain stranded tax effects in accumulated other comprehensive income as a result of the Tax Cuts and Jobs Act of 2017. The guidance is effective for fiscal years beginning after December 15, 2018, including interim periods, therein, and early adoption is permitted. During the quarter ended March 31, 2018, the Company adopted the ASU and made a reclassification adjustment of $1,772,000 to increase accumulated other comprehensive income and decrease retained earnings on the Consolidated Statements of Changes in Stockholders' Equity. In August 2017, the FASB issued ASU 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities. The ASU expands and refines hedge accounting for both financial and non-financial risk components, aligns the recognition and presentation of the effects of hedging instruments and hedge items in the financial statements, and includes certain targeted improvements to ease the application of current guidance related to the assessment of hedge effectiveness. The effective date of the new standard for public companies is for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Early adoption is permitted. The new standard must be adopted using a modified retrospective transition with a cumulative effect adjustment recorded to opening retained earnings as of the initial adoption date. The Company does not anticipate that this guidance will have a material impact on its consolidated financial statements. In March 2017, the FASB issued ASU 2017-08, Receivables - Nonrefundable Fees and Other Costs (Subtopic 310-20), Premium Amortization on Purchased Callable Debt Securities. The ASU shortens the amortization period for certain callable debt securities held at a premium. Specifically, the amendments require the premium to be amortized to the earliest call date. The amendments do not require an accounting change for securities held at a discount; the discount continues to be amortized to maturity. The ASU is effective for public business entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. Early adoption is permitted, including adoption in an interim period. If an entity early adopts in an interim period, any adjustments should be reflected as of the beginning of the fiscal year that includes that interim period. The amendments should be applied on a modified retrospective basis, with a cumulative-effect adjustment directly to retained earnings as of the beginning of the period of adoption. The Company does not anticipate that this guidance will have a material impact on its consolidated financial statements . In February 2017, the FASB issued ASU 2017-05, Other Income - Gains and Losses from the Derecognition of Nonfinancial Assets (Subtopic 610-20): Clarifying the Scope of Asset Derecognition Guidance and Accounting for Partial Sales of Nonfinancial Assets. The ASU clarifies that a financial asset is within the scope of Subtopic 610-20 if it meets the definition of an in substance nonfinancial asset. The amendments also define the term in substance nonfinancial asset. The amendments clarify that nonfinancial assets within the scope of Subtopic 610-20 may include nonfinancial assets transferred within a legal entity to a counterparty. A contract that includes the transfer of ownership interests in one or more consolidated subsidiaries is within the scope of Subtopic 610-20 if substantially all of the fair value of the assets that are promised to the counterparty in a contract is concentrated in nonfinancial assets. The amendments clarify that an entity should identify each distinct nonfinancial asset or in substance nonfinancial asset promised to a counterparty and derecognize each asset when a counterparty obtains control of it. The ASU is effective for public business entities for annual periods beginning after December 15, 2017, and interim periods therein. Entities may use either a full or modified approach to adopt the ASU. The Company does not anticipate that this guidance will have a material impact on its consolidated financial statements. In January 2017, the FASB issued ASU 2017-04, Intangibles - Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment , which eliminates Step 2 from the goodwill impairment test. The ASU also eliminates the requirements for any reporting unit with a zero or negative carrying amount to perform a qualitative assessment and, if it fails that qualitative test, to perform Step 2 of the goodwill impairment test. An entity still has the option to perform the qualitative assessment for a reporting unit to determine if the quantitative impairment test is necessary. The ASU is effective for annual or interim goodwill impairment tests in fiscal years beginning after December 15, 2019, with early adoption being permitted for annual or interim goodwill impairment tests performed on testing dates after January 1, 2017. During the quarter ended March 31, 2018, the Company adopted the ASU and there was no impact on its consolidated financial statements. In January 2017, the FASB issued ASU 2017-01, Business Combinations Clarifying the Definition of a Business (Topic 805) , for determining whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The ASU is effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2017, with early adoption permitted for transactions that occurred before the issuance date or effective date of the standard if the transactions were not reported in financial statements that have been issued or made available for issuance. The ASU must be applied prospectively and upon adoption the standard will impact how we assess acquisitions (or disposals) of assets or businesses. During the quarter ended March 31, 2018, the Company adopted the ASU and there was no impact on its consolidated financial statements. In November 2016, the FASB issued ASU 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash: a Consensus of the FASB Emerging Issues Task Force . This ASU requires a company’s cash flow statement to explain the changes during a reporting period of the totals for cash, cash equivalents, restricted cash, and restricted cash equivalents. Additionally, amounts for restricted cash and restricted cash equivalents are to be included with cash and cash equivalents if the cash flow statement includes a reconciliation of the total cash balances for a reporting period. This ASU is effective for public business entities for annual periods, including interim periods within those annual periods, beginning after December 15, 2017, with early application permitted. The Company does not anticipate that this guidance will have a material impact on its consolidated financial statements. In August 2016, the FASB issued ASU 2016-15, Classification of Certain Cash Receipts and Cash Payments. The amendments in this ASU address eight specific cash flow issues with the objective of reducing diversity in practice. The specific issues identified include: debt prepayments or extinguishment costs; contingent consideration payments made after a business combination; proceeds from the settlement of insurance claims; proceeds from the settlement of corporate-owned life insurance policies (including bank-owned life insurance policies); distributions received from equity method investees; beneficial interests in securitization transactions; and separately identifiable cash flows and application of the predominance principle. This ASU is effective for fiscal years beginning after December 15, 2017, including interim periods within that reporting period; however, early adoption is permitted. The Company is currently evaluating the guidance to determine its adoption method and does not expect this guidance to have a material impact on its consolidated financial statements. In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses . The amendments in this ASU were issued to provide financial statement users with more decision-useful information about the expected credit losses on financial instruments that are not accounted for at fair value through net income, including loans held for investment, held-to-maturity debt securities, trade and other receivables, net investments in leases and other commitments to extend credit held by a reporting entity at each reporting date. The amendments require that financial assets measured at amortized cost be presented at the net amount expected to be collected, through an allowance for credit losses that is deducted from the amortized cost basis. The ASU eliminates the current framework of recognizing probable incurred losses and instead requires an entity to use its current estimate of all expected credit losses over the contractual life. The measurement of expected credit losses is based upon historical experience, current conditions, and reasonable and supportable forecasts that affect the collectability of the financial assets. For purchased financial assets with a more-than-insignificant amount of credit deterioration since origination (“PCD assets”) that are measured at amortized cost, an allowance for expected credit losses is recorded as an adjustment to the cost basis of the asset. Subsequent changes in estimated cash flows would be recorded as an adjustment to the allowance and through the statement of income. Credit losses relating to available-for-sale debt securities will be recorded through an allowance for credit losses rather than as a direct write-down to the security's cost basis. The amendments in this ASU are effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. For most debt securities, the transition approach requires a cumulative-effect adjustment to the statement of financial position as of the beginning of the first reporting period the guidance is effective. For other-than-temporarily impaired debt securities and PCD assets, the guidance will be applied prospectively. While the Company is currently in the process of evaluating the impact of the amended guidance on its consolidated financial statements, it currently expects the ALLL to increase upon adoption given that the allowance will be required to cover the full remaining expected life of the portfolio upon adoption, rather than the incurred loss model under current U.S. GAAP. The extent of this increase is still being evaluated and will depend on economic conditions and the composition of the Company’s loan and lease portfolio at the time of adoption. In February 2016, the FASB issued ASU 2016-02, Leases . The amendments require lessees to recognize a lease liability, which is a lessee's obligation to make lease payments arising from a lease, and a right-of-use asset, which is an asset that represents the lessee's right to use, or control the use of, a specified asset for the lease term. The guidance also simplifies the accounting for sale and leaseback transactions. The amendments are effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. Early application is permitted upon issuance. Lessees (for capital and operating leases) and lessors (for sales-type, direct financing, and operating leases) must apply a modified retrospective transition approach for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. The modified retrospective approach would not require any transition accounting for leases that expired before the earliest comparative period presented. Lessees and lessors may not apply a full retrospective transition approach. The Company is currently in the process of accumulating the lease data necessary to apply the amended guidance. The Company is continuing to evaluate the impact of the amended guidance on its consolidated financial statements, but the effects of recognizing most operating leases is not expected to be material. The Company expects to recognize right-of-use assets and lease liabilities for substantially all of its operating lease commitments based on the present value of unpaid lease payments as of the date of adoption. In January 2016, the FASB issued ASU 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities , to require all equity investments to be measured at fair value with changes in the fair value recognized through net income (other than those accounted for under equity method of accounting or those that result in consolidation of the investee). The amendments in this ASU also require an entity to present separately in other comprehensive income the portion of the total change in the fair value of a liability resulting from a change in the instrument-specific credit risk when the entity has elected to measure the liability at fair value in accordance with the fair value option for financial instruments. This ASU is effective for fiscal years beginning after December 15, 2017, including interim periods within that reporting period. The Company does not expect this guidance to have a material impact on its consolidated financial statements. In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606) . The guidance in this update supersedes the revenue recognition requirements in ASC Topic 605, Revenue Recognition, and most industry-specific guidance throughout the industry topics of the codification. For public companies, this update was to be effective for interim and annual periods beginning after December 15, 2016. However, in August 2015, the FASB issued ASU 2015-14, which delayed the effective date of ASU 2014-09 by one year and permits companies to voluntarily adopt the new standard as of the original effective date. The Company does not expect this guidance to have a material impact on its consolidated financial statements.

Dividends and Share Repurchases

Dividends and Share Repurchases	6 Months Ended
	Mar. 31, 2018
Dividends [Abstract]
Dividends and Share Repurchases	Dividends and Share Repurchases On February 23, 2018 , the Company paid a regular dividend on common stock of $0.17 per share, which represented the 140th consecutive quarterly cash dividend. Dividends per share were $ 0.17 and $ 0.40 for the quarters ended March 31, 2018 and 2017 , respectively. On April 30, 2018 , the Company declared a regular dividend on common stock of $0.17 per share, which represents its 141st consecutive quarterly cash dividend. This dividend will be paid on May 25, 2018 to common shareholders of record on May 11, 2018 . For the three months ended March 31, 2018 , the Company repurchased 1,673,436 shares at an average price of $34.66 . No shares of common stock were issued during the three months ended March 31, 2018 to investors holding warrants previously issued as part of the 2008 Troubled Asset Relief Program ("TARP"). As of March 31, 2018 , 112,649 such warrants remain outstanding. Net of warrant cash repurchase activity, there are 4,080,149 remaining shares authorized to be repurchased under the current Board approved share repurchase program.

Loans Receivable

Loans Receivable	6 Months Ended
	Mar. 31, 2018
Receivables [Abstract]
Loans Receivable	Loans Receivable The following table is a summary of loans receivable. March 31, 2018 September 30, 2017 (In thousands) (In thousands) Gross loans by category Single-family residential $ 5,705,350 45.5 % $ 5,711,004 46.8 % Construction 1,732,202 13.8 1,597,996 13.1 Construction - custom 597,671 4.8 602,631 4.9 Land - acquisition & development 141,628 1.1 124,308 1.0 Land - consumer lot loans 102,779 0.8 104,405 0.9 Multi-family 1,328,049 10.6 1,303,148 10.7 Commercial real estate 1,443,437 11.5 1,434,610 11.8 Commercial & industrial 1,151,108 9.2 1,093,360 9.0 HELOC 135,119 1.1 144,850 1.2 Consumer 202,911 1.6 85,075 0.7 Total gross loans 12,540,254 100 % 12,201,387 100 % Less: Allowance for loan losses 127,576 123,073 Loans in process 1,141,018 1,149,934 Net deferred fees, costs and discounts 47,572 45,758 Total loan contra accounts 1,316,166 1,318,765 Net loans $ 11,224,088 $ 10,882,622 The following table sets forth information regarding non-accrual loans. March 31, 2018 September 30, 2017 (In thousands) Non-accrual loans: Single-family residential $ 25,319 47.1 % $ 27,930 56.3 % Construction 2,296 4.3 — — Construction - custom — — 91 0.2 Land - acquisition & development 2,004 3.7 296 0.6 Land - consumer lot loans 1,045 1.9 605 1.2 Multi-family — — 139 0.3 Commercial real estate 9,527 17.7 11,815 23.8 Commercial & industrial 13,362 24.8 8,082 16.3 HELOC 217 0.4 531 1.1 Consumer 38 0.1 91 0.2 Total non-accrual loans $ 53,808 100 % $ 49,580 100 % % of total net loans 0.48 % 0.46 % The Company recognized interest income on non-accrual loans of approximately $3,228,000 in the six months ended March 31, 2018 . Had these loans been on accrual status and performed according to their original contract terms, the Company would have recognized interest income of approximately $1,073,000 for the six months ended March 31, 2018 . Interest cash flows collected on non-accrual loans vary from period to period as those loans are brought current or are paid off. The following tables provide details regarding delinquent loans. March 31, 2018 Loans Receivable Days Delinquent Based on $ Amount of Loans % based on $ Type of Loan Net of Loans In Process Current 30 60 90 Total Delinquent (In thousands) Single-family residential $ 5,704,505 $ 5,675,605 $ 6,268 $ 3,621 $ 19,011 $ 28,900 0.51 % Construction 916,662 913,419 948 — 2,295 3,243 0.35 Construction - custom 295,699 295,699 — — — — — Land - acquisition & development 119,063 117,200 — — 1,863 1,863 1.56 Land - consumer lot loans 102,705 101,837 328 — 540 868 0.85 Multi-family 1,328,027 1,327,864 29 134 — 163 0.01 Commercial real estate 1,443,437 1,441,459 1,275 98 605 1,978 0.14 Commercial & industrial 1,151,108 1,143,385 1,850 5,752 121 7,723 0.67 HELOC 135,119 134,866 163 30 60 253 0.19 Consumer 202,911 202,413 348 127 23 498 0.25 Total Loans $ 11,399,236 $ 11,353,747 $ 11,209 $ 9,762 $ 24,518 $ 45,489 0.40 % Delinquency % 99.60% 0.10% 0.09% 0.22% 0.40% September 30, 2017 Loans Receivable Days Delinquent Based on $ Amount of Loans % based on $ Type of Loan Net of Loans In Process Current 30 60 90 Total Delinquent (In thousands) Single-family residential $ 5,709,690 $ 5,671,933 $ 10,925 $ 4,810 $ 22,022 $ 37,757 0.66 % Construction 793,959 793,959 — — — — — Construction - custom 277,599 277,508 — — 91 91 0.03 Land - acquisition & development 104,856 104,526 — — 330 330 0.31 Land - consumer lot loans 104,335 103,389 112 680 154 946 0.91 Multi-family 1,303,119 1,302,720 5 255 139 399 0.03 Commercial real estate 1,434,610 1,432,052 507 — 2,051 2,558 0.18 Commercial & industrial 1,093,360 1,092,735 — 51 574 625 0.06 HELOC 144,850 143,974 221 342 313 876 0.60 Consumer 85,075 84,644 245 107 79 431 0.51 Total Loans $ 11,051,453 $ 11,007,440 $ 12,015 $ 6,245 $ 25,753 $ 44,013 0.40 % Delinquency % 99.60% 0.11% 0.06% 0.23% 0.40% The percentage of total delinquent loans was 0.40% as of September 30, 2017 and 0.40% as of March 31, 2018 . There are no loans greater than 90 days delinquent and still accruing interest as of either date. The following table provides information related to loans that were restructured in a troubled debt restructuring ("TDR") during the periods presented: Three Months Ended March 31, 2018 2017 Pre-Modification Post-Modification Pre-Modification Post-Modification Outstanding Outstanding Outstanding Outstanding Number of Recorded Recorded Number of Recorded Recorded Contracts Investment Investment Contracts Investment Investment (In thousands) (In thousands) Troubled Debt Restructurings: Single-family residential 12 $ 2,183 $ 2,183 8 $ 1,712 $ 1,712 12 $ 2,183 $ 2,183 8 $ 1,712 $ 1,712 Six Months Ended March 31, 2018 2017 Pre-Modification Post-Modification Pre-Modification Post-Modification Outstanding Outstanding Outstanding Outstanding Number of Recorded Recorded Number of Recorded Recorded Contracts Investment Investment Contracts Investment Investment (In thousands) (In thousands) Troubled Debt Restructurings: Single-family residential 20 $ 4,195 $ 4,195 20 $ 3,846 $ 3,846 Land - consumer lot loans — — — 1 204 204 Commercial & Industrial 3 7,256 7,256 — — — HELOC — — — 1 228 228 23 $ 11,451 $ 11,451 22 $ 4,278 $ 4,278 The following table provides information on payment defaults occurring during the periods presented where the loan had been modified in a TDR within 12 months of the payment default. Three Months Ended March 31, 2018 2017 Number of Recorded Number of Recorded Contracts Investment Contracts Investment (In thousands) (In thousands) Trouble Debt Restructurings That Subsequently Defaulted: Single-family residential 1 $ 162 7 $ 1,192 1 $ 162 7 $ 1,192 Six Months Ended March 31, 2018 2017 Number of Recorded Number of Recorded Contracts Investment Contracts Investment (In thousands) (In thousands) Troubled Debt Restructurings That Subsequently Defaulted: Single-family residential 2 $ 206 13 $ 3,185 Commercial real estate — — 2 267 2 $ 206 15 $ 3,452 Most loans restructured in TDRs are accruing and performing loans where the borrower has proactively approached the Company about modification due to temporary financial difficulties. As of March 31, 2018 , 97.7% of the Company's $190,519,000 in TDRs were classified as performing. Each request for modification is individually evaluated for merit and likelihood of success. The concession granted in a loan modification is typically a payment reduction through a rate reduction of between 100 to 200 basis points for a specific term, usually six to twenty four months. Interest-only payments may also be approved during the modification period. Principal forgiveness is not an available option for restructured loans. As of March 31, 2018 , single-family residential loans comprised 85.5% of TDRs. The Company reserves for restructured loans within its allowance for loan loss methodology by taking into account the following performance indicators: 1) time since modification, 2) current payment status and 3) geographic area. The Company's remaining outstanding balance of assets subject to FDIC loss share agreements was $54,626,000 (including $50,777,000 of loans receivable) at March 31, 2018 compared to $67,914,000 (including $61,810,000 of loans receivable) as of September 30, 2017 . As of March 31, 2018 , the associated FDIC indemnification asset was $0 compared to a balance of $8,967,000 as of September 30, 2017 . The FDIC clawback liability was $39,906,000 as of March 31, 2018 and $37,143,000 as of September 30, 2017 . In March 2018, the Company reached a preliminary agreement with the FDIC to terminate its remaining FDIC loss share agreements early, which relate to the Horizon Bank and Home Valley Bank acquisitions. The preliminary agreement is consistent with the estimates recorded by the Company as of December 31, 2017 and final settlement is expected to occur in the third fiscal quarter of 2018. All future recoveries, gains, losses and expenses related to the previously covered assets will now be recognized entirely by the Company and the FDIC will no longer share in such gains or losses.

Allowance for Losses on Loans

Allowance for Losses on Loans	6 Months Ended
	Mar. 31, 2018
Receivables [Abstract]
Allowance for Losses on Loans	Allowance for Losses on Loans The following tables summarize the activity in the allowance for loan losses. Three Months Ended March 31, 2018 Beginning Allowance Charge-offs Recoveries Provision & Transfers Ending Allowance (In thousands) Single-family residential $ 35,928 $ (290 ) $ 211 $ (1,705 ) $ 34,144 Construction 25,214 — — 2,175 27,389 Construction - custom 2,052 — — 29 2,081 Land - acquisition & development 7,355 — 1,207 (940 ) 7,622 Land - consumer lot loans 2,906 (18 ) — (35 ) 2,853 Multi-family 7,904 — — 78 7,982 Commercial real estate 11,625 (36 ) 1 (2 ) 11,588 Commercial & industrial 29,268 — 115 (53 ) 29,330 HELOC 808 (1 ) — (5 ) 802 Consumer 4,095 (94 ) 276 (492 ) 3,785 $ 127,155 $ (439 ) $ 1,810 $ (950 ) $ 127,576 Three Months Ended March 31, 2017 Beginning Allowance Charge-offs Recoveries Provision & Transfers Ending Allowance (In thousands) Single-family residential $ 38,206 $ (381 ) $ 223 $ (884 ) $ 37,164 Construction 21,934 — — 3,127 25,061 Construction - custom 1,110 (3 ) — 69 1,176 Land - acquisition & development 6,665 (43 ) 4,211 (4,164 ) 6,669 Land - consumer lot loans 2,501 — 180 (168 ) 2,513 Multi-family 7,629 — — 300 7,929 Commercial real estate 10,168 — 1,164 (560 ) 10,772 Commercial & industrial 27,736 (105 ) 217 517 28,365 HELOC 832 (53 ) — 47 826 Consumer 1,675 (508 ) 314 (34 ) 1,447 $ 118,456 $ (1,093 ) $ 6,309 $ (1,750 ) $ 121,922 Six Months Ended March 31, 2018 Beginning Allowance Charge-offs Recoveries Provision & Transfers Ending Allowance (In thousands) Single-family residential $ 36,892 $ (750 ) $ 331 $ (2,329 ) $ 34,144 Construction 24,556 — — 2,833 27,389 Construction - custom 1,944 (50 ) — 187 2,081 Land - acquisition & development 6,829 — 4,579 (3,786 ) 7,622 Land - consumer lot loans 2,649 (66 ) — 270 2,853 Multi-family 7,862 — — 120 7,982 Commercial real estate 11,818 (36 ) 1 (195 ) 11,588 Commercial & industrial 28,524 (116 ) 170 752 29,330 HELOC 855 (1 ) 1 (53 ) 802 Consumer 1,144 (172 ) 562 2,251 3,785 $ 123,073 $ (1,191 ) $ 5,644 $ 50 $ 127,576 Six Months Ended March 31, 2017 Beginning Allowance Charge-offs Recoveries Provision & Transfers Ending Allowance (In thousands) Single-family residential $ 37,796 $ (496 ) $ 374 $ (510 ) $ 37,164 Construction 19,838 — — 5,223 25,061 Construction - custom 1,080 (3 ) — 99 1,176 Land - acquisition & development 6,023 (63 ) 8,229 (7,520 ) 6,669 Land - consumer lot loans 2,535 (17 ) 250 (255 ) 2,513 Multi-family 6,925 — — 1,004 7,929 Commercial real estate 8,588 (11 ) 1,520 675 10,772 Commercial & industrial 28,008 (163 ) 942 (422 ) 28,365 HELOC 813 (90 ) 1 102 826 Consumer 1,888 (654 ) 693 (480 ) 1,447 $ 113,494 $ (1,497 ) $ 12,009 $ (2,084 ) $ 121,922 The Company recorded a release of allowance for loan losses of $950,000 for the three months ended March 31, 2018 , compared to a $1,600,000 release of allowance for loan losses for the three months ended March 31, 2017 . A release of allowance for loan losses of $950,000 and $1,600,000 was recorded during the six months ended March 31, 2018 and March 31, 2017 , respectively. Reserving for new loan originations as the loan portfolio grows has been largely offset by recoveries of previously charged-off loans. Recoveries, net of charge-offs, totaled $1,371,000 for the three months ended March 31, 2018 , compared to net recoveries of $5,216,000 during the three months ended March 31, 2017 . Recoveries, net of charge-offs, totaled $4,453,000 for the six months ended March 31, 2018 , compared to net recoveries of $10,512,000 during the six months ended March 31, 2017 . Non-performing assets were $69,712,000 , or 0.45% , of total assets at March 31, 2018 , compared to $70,238,000 , or 0.46% , of total assets at September 30, 2017 . Non-accrual loans were $53,808,000 at March 31, 2018 , compared to $49,580,000 at September 30, 2017 . Delinquencies, as a percent of total loans, were 0.40% at March 31, 2018 , compared to 0.40% at September 30, 2017 . The reserve for unfunded commitments was $6,750,000 as of March 31, 2018 , which is a decrease from $7,750,000 at September 30, 2017 . Management believes the allowance for loan losses plus the reserve for unfunded commitments, totaling $134,326,000 , or 1.07% of gross loans as of March 31, 2018 , is sufficient to absorb estimated inherent losses. The following tables show loans collectively and individually evaluated for impairment and the related allocation of general and specific reserves. March 31, 2018 Loans Collectively Evaluated for Impairment Loans Individually Evaluated for Impairment Allowance Allocation Recorded Investment of Loans Ratio Allowance Allocation Recorded Investment of Loans Ratio (In thousands) (In thousands) Single-family residential $ 34,144 $ 5,684,940 0.6 % $ — $ 27,608 — % Construction 27,389 911,650 3.0 — 5,012 — Construction - custom 2,081 295,699 0.7 — — — Land - acquisition & development 7,622 116,877 6.5 — 2,186 — Land - consumer lot loans 2,853 95,482 3.0 — 495 — Multi-family 7,978 1,324,959 0.6 4 3,068 0.1 Commercial real estate 11,484 1,385,851 0.8 104 39,861 0.3 Commercial & industrial 28,784 1,114,171 2.6 546 36,888 1.5 HELOC 802 133,152 0.6 — 273 — Consumer 3,785 202,766 1.9 — 38 — $ 126,922 $ 11,265,547 1.1 % $ 654 $ 115,429 0.6 % September 30, 2017 Loans Collectively Evaluated for Impairment Loans Individually Evaluated for Impairment Allowance Allocation Recorded Investment of Loans Ratio Allowance Allocation Recorded Investment of Loans Ratio (In thousands) (In thousands) Single-family residential $ 36,892 $ 5,713,576 0.7 % $ — $ 5,552 — % Construction 24,556 793,958 3.1 — — — Construction - custom 1,944 277,495 0.7 — 105 — Land - acquisition & development 6,828 104,767 6.5 1 89 1.0 Land - consumer lot loans 2,649 96,337 2.8 — 171 — Multi-family 7,857 1,302,625 0.6 5 493 1.0 Commercial real estate 11,698 1,391,668 0.8 120 21,765 0.6 Commercial & industrial 28,524 1,093,210 2.6 — 81 — HELOC 855 141,689 0.6 — 215 — Consumer 1,144 84,887 1.4 — 82 — $ 122,947 $ 11,000,212 1.1 % $ 126 $ 28,553 0.4 % As of March 31, 2018 , $126,922,000 of the allowance was calculated under the formulas contained in our general allowance methodology and the remaining $654,000 was specific reserves on loans deemed to be individually impaired. As of September 30, 2017 , $122,947,000 of the allowance was calculated under the formulas contained in our general allowance methodology and the remaining $126,000 was specific reserves on loans deemed to be individually impaired. The Company has an asset quality review function that analyzes its loan portfolio and reports the results of the review to the Board of Directors on a quarterly basis. The single-family residential, HELOC and consumer portfolios are evaluated based on their performance as a pool of loans, since no single loan is individually significant or judged by its risk rating, size or potential risk of loss. The construction, land, multi-family, commercial real estate and commercial and industrial loans are risk rated on a loan by loan basis to determine the relative risk inherent in specific borrowers or loans. Based on that risk rating, the loans are assigned a grade and classified as follows: • Pass – the credit does not meet one of the definitions below. • Special mention – A special mention credit is considered to be currently protected from loss but is potentially weak. No loss of principal or interest is foreseen; however, proper supervision and Management attention is required to deter further deterioration in the credit. Assets in this category constitute some undue and unwarranted credit risk but not to the point of justifying a risk rating of substandard. The credit risk may be relatively minor yet constitutes an unwarranted risk in light of the circumstances surrounding a specific asset. • Substandard – A substandard credit is an unacceptable credit. Additionally, repayment in the normal course is in jeopardy due to the existence of one or more well defined weaknesses. In these situations, loss of principal is likely if the weakness is not corrected. A substandard asset is inadequately protected by the current sound worth and paying capacity of the borrower or of the collateral pledged, if any. Assets so classified will have a well-defined weakness or weaknesses that jeopardize the collection or liquidation of the debt. Loss potential, while existing in the aggregate amount of substandard assets, does not have to exist in individual assets risk rated substandard. • Doubtful – A credit classified doubtful has all the weaknesses inherent in one classified substandard with the added characteristic that the weakness makes collection or liquidation in full, on the basis of currently existing facts, conditions and values, highly questionable and improbable. The probability of loss is high, but because of certain important and reasonably specific pending factors that may work to the advantage and strengthening of the asset, its classification as an estimated loss is deferred until its more exact status may be determined. Pending factors include proposed merger, acquisition, or liquidation procedures, capital injection, perfecting liens on additional collateral, and refinancing plans. • Loss – Credits classified loss are considered uncollectible and of such little value that their continuance as a bankable asset is not warranted. This classification does not mean that the asset has absolutely no recovery or salvage value, but rather it is not practical or desirable to defer writing off this asset even though partial recovery may be affected in the future. Losses should be taken in the period in which they are identified as uncollectible. Partial charge-off versus full charge-off may be taken if the collateral offers some identifiable protection. The following tables provide information on loans based on risk rating categories as defined above. March 31, 2018 Internally Assigned Grade Pass Special mention Substandard Doubtful Loss Total Gross Loans (In thousands) Loan type Single-family residential $ 5,670,826 $ — $ 34,524 $ — $ — $ 5,705,350 Construction 1,727,190 — 5,012 — — 1,732,202 Construction - custom 597,671 — — — — 597,671 Land - acquisition & development 139,442 — 2,186 — — 141,628 Land - consumer lot loans 101,733 — 1,046 — — 102,779 Multi-family 1,325,076 379 2,594 — — 1,328,049 Commercial real estate 1,410,194 634 32,609 — — 1,443,437 Commercial & industrial 1,101,878 9,958 39,272 — — 1,151,108 HELOC 134,763 — 356 — — 135,119 Consumer 202,873 — 38 — — 202,911 Total gross loans $ 12,411,646 $ 10,971 $ 117,637 $ — $ — $ 12,540,254 Total grade as a % of total gross loans 99.0 % 0.1 % 0.9 % — % — % September 30, 2017 Internally Assigned Grade Pass Special mention Substandard Doubtful Loss Total Gross Loans (In thousands) Loan type Single-family residential $ 5,671,229 $ — $ 39,775 $ — $ — $ 5,711,004 Construction 1,594,926 — 3,070 — — 1,597,996 Construction - custom 602,540 — 91 — — 602,631 Land - acquisition & development 123,028 207 1,073 — — 124,308 Land - consumer lot loans 103,787 — 618 — — 104,405 Multi-family 1,295,261 5,795 2,092 — — 1,303,148 Commercial real estate 1,391,996 5,944 36,670 — — 1,434,610 Commercial & industrial 1,054,972 14,814 23,574 — — 1,093,360 HELOC 144,229 — 621 — — 144,850 Consumer 84,984 — 91 — — 85,075 Total gross loans $ 12,066,952 $ 26,760 $ 107,675 $ — $ — $ 12,201,387 Total grade as a % of total gross loans 98.9 % 0.2 % 0.9 % — % — % The following tables provide information on gross loans based on borrower payment activity. March 31, 2018 Performing Loans Non-Performing Loans Amount % of Total Gross Loans Amount % of Total Gross Loans (In thousands) Single-family residential $ 5,680,031 99.6 % $ 25,319 0.4 % Construction 1,729,906 99.9 2,296 0.1 Construction - custom 597,671 100.0 — — Land - acquisition & development 139,624 98.6 2,004 1.4 Land - consumer lot loans 101,734 99.0 1,045 1.0 Multi-family 1,328,049 100.0 — — Commercial real estate 1,433,910 99.3 9,527 0.7 Commercial & industrial 1,137,746 98.8 13,362 1.2 HELOC 134,902 99.8 217 0.2 Consumer 202,873 100.0 38 — $ 12,486,446 99.6 % $ 53,808 0.4 % September 30, 2017 Performing Loans Non-Performing Loans Amount % of Total Gross Loans Amount % of Total Gross Loans (In thousands) Single-family residential $ 5,683,074 99.5 % $ 27,930 0.5 % Construction 1,597,996 100.0 — — Construction - custom 602,540 99.9 91 0.1 Land - acquisition & development 124,012 99.8 296 0.2 Land - consumer lot loans 103,800 99.4 605 0.6 Multi-family 1,303,009 99.9 139 0.1 Commercial real estate 1,422,795 99.2 11,815 0.8 Commercial & industrial 1,085,278 99.3 8,082 0.7 HELOC 144,319 99.6 531 0.4 Consumer 84,984 99.9 91 0.1 $ 12,151,807 99.6 % $ 49,580 0.4 % The following tables provide information on impaired loan balances and the related allowances by loan types. March 31, 2018 Recorded Investment Unpaid Principal Balance Related Allowance Average Recorded Investment (Year-To-Date) (In thousands) Impaired loans with no related allowance recorded: Single-family residential $ 23,936 $ 25,229 $ — $ 21,889 Construction 5,898 5,898 — 2,289 Construction - custom — — — 49 Land - acquisition & development 2,186 2,230 — 1,297 Land - consumer lot loans 386 432 — 298 Multi-family 2,616 2,616 — 1,002 Commercial real estate 33,272 38,372 — 20,845 Commercial & industrial 29,882 29,989 — 14,200 HELOC 273 366 — 461 Consumer 38 104 — 65 98,487 105,236 — 62,395 Impaired loans with an allowance recorded: Single-family residential 162,875 166,405 2,942 171,831 Land - acquisition & development — — — 30 Land - consumer lot loans 6,837 7,431 — 7,397 Multi-family 473 473 4 482 Commercial real estate 11,818 12,673 104 12,936 Commercial & industrial 7,006 7,006 546 4,754 HELOC 1,424 1,506 — 1,503 Consumer 86 273 — 91 190,519 195,767 3,596 (1) 199,024 Total impaired loans: Single-family residential 186,811 191,634 2,942 193,720 Construction 5,898 5,898 — 2,289 Construction - custom — — — 49 Land - acquisition & development 2,186 2,230 — 1,327 Land - consumer lot loans 7,223 7,863 — 7,695 Multi-family 3,089 3,089 4 1,484 Commercial real estate 45,090 51,045 104 33,781 Commercial & industrial 36,888 36,995 546 18,954 HELOC 1,697 1,872 — 1,964 Consumer 124 377 — 156 $ 289,006 $ 301,003 $ 3,596 (1) $ 261,419 (1) Includes $654,000 of specific reserves and $2,942,000 included in the general reserves. September 30, 2017 Recorded Investment Unpaid Principal Balance Related Allowance Average Recorded Investment (In thousands) Impaired loans with no related allowance recorded: Single-family residential $ 21,325 $ 23,880 $ — $ 19,371 Construction - custom 148 165 — 231 Land - acquisition & development 330 8,208 — 176 Land - consumer lot loans 208 330 — 431 Multi-family 139 3,231 — 748 Commercial real estate 12,890 22,487 — 11,466 Commercial & industrial 8,279 14,321 — 7,425 HELOC 490 1,212 — 487 Consumer 88 1,433 — 57 43,897 75,267 — 40,392 Impaired loans with an allowance recorded: Single-family residential 181,941 186,167 4,030 204,723 Land - acquisition & development 90 90 1 576 Land - consumer lot loans 7,949 8,526 — 8,976 Multi-family 493 493 5 1,024 Commercial real estate 15,079 16,707 120 16,991 Commercial & industrial — — — 297 HELOC 1,728 1,806 — 1,451 Consumer 97 284 — 100 207,377 214,073 4,156 (1) 234,138 Total impaired loans: Single-family residential 203,266 210,047 4,030 224,094 Construction - custom 148 165 — 231 Land - acquisition & development 420 8,298 1 752 Land - consumer lot loans 8,157 8,856 — 9,407 Multi-family 632 3,724 5 1,772 Commercial real estate 27,969 39,194 120 28,457 Commercial & industrial 8,279 14,321 — 7,722 HELOC 2,218 3,018 — 1,938 Consumer 185 1,717 — 157 $ 251,274 $ 289,340 $ 4,156 (1) $ 274,530 (1) Includes $126,000 of specific reserves and $4,030,000 included in the general reserves.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements ASC 820 defines fair value as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. ASC 820 also establishes a fair value hierarchy that requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. The standard describes three levels of inputs that may be used to measure fair value: Level 1: Quoted prices (unadjusted) for identical assets or liabilities in active exchange markets that the entity has the ability to access as of the measurement date. Level 2: Significant other observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active and other inputs that are observable or can be corroborated by observable market data. Level 3: Significant unobservable inputs that reflect a company’s own assumptions about the assumptions that market participants would use in pricing an asset or liability. We have established and documented the Company's process for determining the fair values of the Company's assets and liabilities, where applicable. Fair value is based on quoted market prices, when available, for identical or similar assets or liabilities. In the absence of quoted market prices, fair value is determined using valuation models or third-party appraisals. The following is a description of the valuation methodologies used to measure and report the fair value of financial assets and liabilities on a recurring or nonrecurring basis. Measured on a Recurring Basis Available-for-Sale Securities and Derivative Contracts Securities available for sale are recorded at fair value on a recurring basis. The fair value of debt securities are priced using model pricing based on the securities' relationship to other benchmark quoted prices as provided by an independent third party, and under GAAP are considered a Level 2 input method. Securities that are traded on active exchanges, including the Company's equity securities, are measured using the closing price in an active market and are considered a Level 1 input method. The Company offers interest rate swaps to its variable rate borrowers who want to manage their interest rate risk. At the same time, the Company enters into the opposite trade with a counter party to offset its interest rate risk. The Company has also entered into commercial loan hedges as well as borrowings hedges using interest rate swaps. The fair value of these interest rate swaps are estimated by a third party pricing service using a discounted cash flow technique. These are considered a Level 2 input method. The following tables present the balance of assets and liabilities measured at fair value on a recurring basis. March 31, 2018 Level 1 Level 2 Level 3 Total (In thousands) Financial Assets Available-for-sale securities: Equity securities $ 495 $ — $ — $ 495 U.S. government and agency securities — 183,939 — 183,939 Municipal bonds — 26,196 — 26,196 Corporate debt securities — 183,457 — 183,457 Mortgage-backed securities Agency pass-through certificates — 866,822 — 866,822 Commercial MBS — 8,362 — 8,362 Total available-for-sale securities 495 1,268,776 — 1,269,271 Interest rate contracts — 8,617 — 8,617 Commercial loan hedges — 2,217 — 2,217 Borrowings hedges — 15,328 — 15,328 Total financial assets $ 495 $ 1,294,938 $ — $ 1,295,433 Financial Liabilities Interest rate contracts $ — $ 8,617 $ — $ 8,617 Total financial liabilities $ — $ 8,617 $ — $ 8,617 There were no transfers between, into and/or out of Levels 1, 2 or 3 during the six months ended March 31, 2018 . September 30, 2017 Level 1 Level 2 Level 3 Total (In thousands) Financial Assets Available-for-sale securities: Equity securities $ 522 $ — $ — $ 522 U.S. government and agency securities — 211,077 — 211,077 Municipal bonds — 26,624 — 26,624 Corporate debt securities — 185,298 — 185,298 Mortgage-backed securities Agency pass-through certificates — 834,297 — 834,297 Commercial MBS — 8,391 — 8,391 Total available-for-sale securities 522 1,265,687 — 1,266,209 Interest rate contracts — 1,139 — 1,139 Total financial assets $ 522 $ 1,266,826 $ — $ 1,267,348 Financial Liabilities Interest rate contracts $ — $ 1,139 $ — $ 1,139 Commercial loan hedges — 174 — 174 Borrowings hedges — 1,693 — 1,693 Total financial liabilities $ — $ 3,006 $ — $ 3,006 There were no transfers between, into and/or out of Levels 1, 2 or 3 during the fiscal year ended September 30, 2017 . Measured on a Nonrecurring Basis Impaired Loans & Real Estate Owned Real estate owned ("REO") consists principally of properties acquired through foreclosure. From time to time, and on a nonrecurring basis, adjustments using fair value measurements are recorded to reflect increases or decreases based on the discounted cash flows, the current appraisal or estimated value of the collateral, but only up to the fair value of the real estate owned as of the initial transfer date less selling costs. When management determines that the fair value of the collateral or the real estate owned requires additional adjustments, either as a result of an updated appraised value or when there is no observable market price, the Company classifies the impaired loan or real estate owned as Level 3. Level 3 assets recorded at fair value on a nonrecurring basis at March 31, 2018 included loans for which a specific reserve allowance was established or a partial charge-off was recorded based on the fair value of collateral, as well as real estate owned where the fair value of the property was less than the cost basis. The following tables present the aggregated balance of assets that were measured at fair value on a nonrecurring basis at March 31, 2018 and March 31, 2017 , and the total gains (losses) resulting from those fair value adjustments for the three and six months ended March 31, 2018 and March 31, 2017 . The estimated fair value measurements are shown gross of estimated selling costs. March 31, 2018 Three Months Ended March 31, 2018 Six Months Ended March 31, 2018 Level 1 Level 2 Level 3 Total Total Gains (Losses) (In thousands) Impaired loans (1) $ — $ — $ 7,343 $ 7,343 $ (466 ) $ (973 ) Real estate owned (2) — — 5,520 5,520 (379 ) (559 ) Balance at end of period $ — $ — $ 12,863 $ 12,863 $ (845 ) $ (1,532 ) (1) The gains (losses) represent remeasurements of collateral-dependent loans. (2) The gains (losses) represent aggregate writedowns and charge-offs on REO. March 31, 2017 Three Months Ended March 31, 2017 Six Months Ended March 31, 2017 Level 1 Level 2 Level 3 Total Total Gains (Losses) (In thousands) Impaired loans (1) $ — $ — $ 5,701 $ 5,701 $ (939 ) $ (1,361 ) Real estate owned (2) — — 5,822 5,822 (378 ) (619 ) Balance at end of period $ — $ — $ 11,523 $ 11,523 $ (1,317 ) $ (1,980 ) (1) The gains (losses) represent remeasurements of collateral-dependent loans. (2) The gains (losses) represent aggregate writedowns and charge-offs on REO. Impaired loans - The Company adjusts the carrying amount of impaired loans when there is evidence of probable loss and the expected fair value of the loan is less than its contractual amount. The amount of the impairment may be determined based on the estimated present value of future cash flows or the fair value of the underlying collateral. Impaired loans with a specific reserve allowance based on cash flow analysis or the value of the underlying collateral are classified as Level 3 assets. The evaluations for impairment are prepared by the Problem Loan Review Committee, which is chaired by the Chief Credit Officer and includes the Loan Review manager and Special Credits manager, as well as senior credit officers, division managers and group executives, as applicable. These evaluations are performed in conjunction with the quarterly allowance for loan loss process. Applicable loans that were included in the previous quarter's review are reevaluated and if their values are materially different from the prior quarter evaluation, the underlying information (loan balance and collateral value) are compared. Material differences are evaluated for reasonableness and discussions are held between the relationship manager and their division manager to understand the difference and determine if any adjustment is necessary. The inputs are developed and substantiated on a quarterly basis, based on current borrower developments, market conditions and collateral values. The following methods are used to value impaired loans: • The fair value of the collateral, which may take the form of real estate or personal property, is based on internal estimates, field observations, assessments provided by third-party appraisers and other valuation models. The Company performs or reaffirms valuations of collateral-dependent impaired loans at least annually. Adjustments are made if management believes that more recent information is available and relevant with respect to the fair value of the collateral. • The present value of the expected future cash flows of the loans is used for measurement of non collateral-dependent loans to test for impairment. Real estate owned - When a loan is reclassified from loan status to real estate owned due to the Company taking possession of the collateral, a special credits officer, along with the special credits manager, obtains a valuation, which may include appraisals or third-party price opinions, which is used to establish the fair value of the underlying collateral. The determined fair value, less selling costs, becomes the carrying value of the REO asset. The fair value of REO assets is re-evaluated quarterly and the REO asset is adjusted to reflect the fair value as necessary. After foreclosure, the valuations are updated periodically and current market conditions may require the assets to be written down further or up to the cost basis established on the date of transfer. The carrying balance of REO assets are also written down once a bona fide offer is contractually accepted, through execution of a purchase and sale agreement, where the accepted price is lower than the cost established on the transfer date. Fair Values of Financial Instruments ASC 825 requires disclosure of fair value information about financial instruments, whether or not recognized on the statement of financial condition, for which it is practicable to estimate those values. Certain financial instruments and all non-financial instruments are excluded from the disclosure requirements. Accordingly, the aggregate fair value estimates presented do not reflect the underlying fair value of the Company. Although management is not aware of any factors that would materially affect the estimated fair value amounts presented below, such amounts have not been comprehensively revalued for purposes of these financial statements since the dates shown, and therefore, estimates of fair value subsequent to those dates may differ significantly from the amounts presented below. March 31, 2018 September 30, 2017 Level in Fair Value Hierarchy Carrying Amount Estimated Fair Value Carrying Amount Estimated Fair Value (In thousands) Financial assets Cash and cash equivalents 1 $ 256,808 $ 256,808 $ 313,070 $ 313,070 Available-for-sale securities Equity securities 1 495 495 522 522 U.S. government and agency securities 2 183,939 183,939 211,077 211,077 Municipal bonds 2 26,196 26,196 26,624 26,624 Corporate debt securities 2 183,457 183,457 185,298 185,298 Mortgage-backed securities Agency pass-through certificates 2 866,822 866,822 834,297 834,297 Commercial MBS 2 8,362 8,362 8,391 8,391 Total available-for-sale securities 1,269,271 1,269,271 1,266,209 1,266,209 Held-to-maturity securities Mortgage-backed securities Agency pass-through certificates 2 1,701,566 1,652,787 1,646,856 1,635,913 Commercial MBS 2 15,000 15,000 — — Total held-to-maturity securities 1,716,566 1,667,787 1,646,856 1,635,913 Loans receivable 3 11,224,088 11,514,350 10,882,622 11,247,586 FDIC indemnification asset 3 — — 8,968 8,564 FHLB and FRB stock 2 126,990 126,990 122,990 122,990 Other assets - interest rate contracts 2 8,617 8,617 1,139 1,139 Other assets - commercial loan hedges 2 2,217 2,217 — — Other assets - borrowings hedges 2 15,328 15,328 — — Financial liabilities Customer accounts 2 11,138,856 10,627,045 10,835,008 10,411,686 FHLB advances 2 2,325,000 2,327,701 2,225,000 2,266,791 Other liabilities - interest rate contracts 2 8,617 8,617 1,139 1,139 Other liabilities - commercial loan hedges 2 — — 174 174 Other liabilities - borrowings hedges 2 — — 1,693 1,693 The following methods and assumptions were used to estimate the fair value of financial instruments: Cash and cash equivalents – The carrying amount of these items is a reasonable estimate of their fair value. Available-for-sale securities and held-to-maturity securities – Securities at fair value are primarily priced using model pricing based on the securities' relationship to other benchmark quoted prices as provided by an independent third party, and are considered a Level 2 input method. Equity securities that are exchange traded are considered a Level 1 input method. Loans receivable – For certain homogeneous categories of loans, such as fixed- and variable-rate residential mortgages, fair value is estimated for securities backed by similar loans, adjusted for differences in loan characteristics, using the same methodology described above for AFS and HTM securities. The fair value of other loan types is estimated by discounting the future cash flows and estimated prepayments using the current rates at which similar loans would be made to borrowers with similar credit ratings and for the same remaining term. Some loan types were valued at carrying value because of their floating rate or expected maturity characteristics. Net deferred loan fees are not included in the fair value calculation but are included in the carrying amount. FHLB and FRB stock – The fair value is based upon the par value of the stock that equates to its carrying value. Customer accounts – The fair value of demand deposits, savings accounts, and money market accounts is the amount payable on demand at the reporting date. The fair value of fixed-maturity certificates of deposit is estimated by discounting the estimated future cash flows using the rates currently offered for deposits with similar remaining maturities. FHLB advances – The fair value of FHLB advances and other borrowings is estimated by discounting the estimated future cash flows using rates currently available to the Company for debt with similar remaining maturities. Interest rate contracts – The bank offers interest rate swaps to its variable rate borrowers who want to manage their interest rate risk. At the same time, the bank enters into the opposite trade with a counterparty to offset its interest rate risk. The fair value of these interest rate swaps is estimated by a third party pricing service using a discounted cash flow technique. Commercial loan hedges – The fair value of the interest rate swaps is estimated by a third party pricing service using a discounted cash flow technique. Borrowings hedges – The fair value of the interest rate swaps is estimated by a third party pricing service using a discounted cash flow technique. The following tables provide a reconciliation of amortized cost to fair value of available-for-sale and held-to-maturity securities. March 31, 2018 Amortized Cost Gross Unrealized Fair Value Yield Gains Losses (In thousands) Available-for-sale securities U.S. government and agency securities due Within 1 year $ 3,300 $ 3 $ — $ 3,303 9.80 % 5 to 10 years 65,997 — (1,432 ) 64,565 2.33 Over 10 years 116,463 27 (419 ) 116,071 2.46 Equity securities due 1 to 5 years 500 — (5 ) 495 1.80 Corporate debt securities due 1 to 5 years 63,692 1,768 — 65,460 3.63 5 to 10 years 119,963 78 (2,044 ) 117,997 2.93 Municipal bonds due Within 1 year 2,359 — (2 ) 2,357 1.23 1 to 5 years 1,382 — (10 ) 1,372 2.05 Over 10 years 20,333 2,134 — 22,467 6.45 Mortgage-backed securities Agency pass-through certificates 870,741 3,400 (7,319 ) 866,822 3.24 Commercial MBS 8,350 12 — 8,362 3.85 1,273,080 7,422 (11,231 ) 1,269,271 3.18 Held-to-maturity securities Mortgage-backed securities Agency pass-through certificates 1,701,566 1,112 (49,891 ) 1,652,787 3.16 Commercial MBS 15,000 — — 15,000 2.66 1,716,566 1,112 (49,891 ) 1,667,787 3.16 $ 2,989,646 $ 8,534 $ (61,122 ) $ 2,937,058 3.17 % September 30, 2017 Amortized Cost Gross Unrealized Fair Value Yield Gains Losses (In thousands) Available-for-sale securities U.S. government and agency securities due Within 1 year $ 9,300 $ 146 $ — $ 9,446 10.38 % 1 to 5 years 5,688 2 — 5,690 1.51 5 to 10 years 69,108 — (1,238 ) 67,870 1.93 Over 10 years 127,936 353 (218 ) 128,071 1.92 Equity securities 1 to 5 years 500 22 — 522 1.80 Corporate bonds due 1 to 5 years 63,622 2,083 — 65,705 2.96 5 to 10 years 119,960 210 (577 ) 119,593 2.62 Municipal bonds due Within 1 year 2,344 10 — 2,354 1.23 1 to 5 years 1,367 55 — 1,422 2.05 Over 10 years 20,343 2,505 — 22,848 6.45 Mortgage-backed securities Agency pass-through certificates 828,069 8,402 (2,174 ) 834,297 2.96 Commercial MBS 8,350 41 — 8,391 3.31 1,256,587 13,829 (4,207 ) 1,266,209 2.86 Held-to-maturity securities Mortgage-backed securities Agency pass-through certificates 1,646,856 7,143 (18,086 ) 1,635,913 3.14 1,646,856 7,143 (18,086 ) 1,635,913 3.14 $ 2,903,443 $ 20,972 $ (22,293 ) $ 2,902,122 3.02 % For available-for-sale investment securities, there were no sales during the six months ended March 31, 2018 and sales totaling $350,890,000 during the six months ended March 31, 2017 . There were purchases of $123,324,000 of available-for-sale investment securities during the six months ended March 31, 2018 and no purchases during the six months ended March 31, 2017 . For held-to-maturity investment securities, there were purchases totaling $170,836,000 during the six months ended March 31, 2018 and purchases of $415,729,000 during the six months ended March 31, 2017 . There were no sales of held-to-maturity investment securities during either period. Substantially all of the agency mortgage-backed securities have contractual due dates that exceed 10 years . The following tables show the unrealized gross losses and fair value of securities as of March 31, 2018 and September 30, 2017 , by length of time that individual securities in each category have been in a continuous loss position. The decline in fair value since purchase is attributable to changes in interest rates. Because the Company does not intend to sell these securities and does not consider it more likely than not that it will be required to sell these securities before the recovery of amortized cost basis, which may be upon maturity, the Company does not consider these investments to be other than temporarily impaired. March 31, 2018 Less than 12 months 12 months or more Total Unrealized Gross Losses Fair Value Unrealized Gross Losses Fair Value Unrealized Gross Losses Fair Value (In thousands) Corporate debt securities $ — $ — $ (2,044 ) $ 97,956 $ (2,044 ) 97,956 Municipal bonds (12 ) 3,729 — — (12 ) 3,729 U.S. government and agency securities — — (1,851 ) 164,140 (1,851 ) 164,140 Equity securities (5 ) 495 — — (5 ) 495 Agency pass-through certificates (8,768 ) 583,301 (48,442 ) 1,428,150 (57,210 ) 2,011,451 $ (8,785 ) $ 587,525 $ (52,337 ) $ 1,690,246 $ (61,122 ) $ 2,277,771 September 30, 2017 Less than 12 months 12 months or more Total Unrealized Gross Losses Fair Value Unrealized Gross Losses Fair Value Unrealized Gross Losses Fair Value (In thousands) Corporate debt securities $ — $ — $ (577 ) $ 49,423 $ (577 ) $ 49,423 U.S. government and agency securities (759 ) 24,400 (697 ) 96,195 (1,456 ) 120,595 Agency pass-through certificates (17,683 ) 1,163,358 (2,577 ) 249,304 (20,260 ) 1,412,662 $ (18,442 ) $ 1,187,758 $ (3,851 ) $ 394,922 $ (22,293 ) $ 1,582,680

Derivatives and Hedging Activit

Derivatives and Hedging Activities	6 Months Ended
	Mar. 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivatives and Hedging Activities	Derivatives and Hedging Activities The Company periodically enters into certain interest rate swap agreements in order to provide commercial loan customers the ability to convert from variable to fixed interest rate payments, while the Company retains a variable rate loan. Under these agreements, the Company enters into a variable rate loan agreement and a swap agreement with the client. The swap agreement effectively converts the client’s variable rate loan into a fixed rate. The Company enters into a corresponding swap agreement with a third party in order to offset its exposure on the variable and fixed components of the client's swap agreement. The Company had $808,981,000 and $1,035,573,000 notional in interest rate swaps to hedge this exposure as of March 31, 2018 and September 30, 2017 , respectively. The interest rate swaps are derivatives under FASB ASC 815, Derivatives and Hedging , with changes in fair value recorded in earnings. There was no net impact to the statement of operations for the six months ended March 31, 2018 and 2017 as the changes in value for the asset and liability side of the swaps offset each other. The Company has entered into interest rate swaps to convert certain existing and future short-term borrowings to fixed rate payments. The primary purpose of these hedges is to mitigate the risk of rising interest rates, specifically LIBOR rates, which are a benchmark for the short-term borrowings. The hedging program qualifies as a cash flow hedge under ASC 815, which provides for offsetting of the recognition of gains and losses of the interest rate swaps and the hedged items. The hedged item is the LIBOR portion of the series of existing or future short-term fixed rate borrowings over the term of the interest rate swap. The change in the fair value of the interest rate swaps is recorded in other comprehensive income. The Company had $700,000,000 notional in interest rate swaps to hedge existing and anticipated future borrowings as of March 31, 2018 and September 30, 2017 . The Company also enters into interest rate swaps to hedge the interest rate risk of individual fixed rate commercial loans and these relationships qualify as fair value hedges under ASC 815, which provides for offsetting of the recognition of gains and losses of the respective interest rate swap and the hedged item. The interest rate swaps in these hedging relationships had a notional amount of $97,927,000 and $52,936,000 as of March 31, 2018 and September 30, 2017 , respectively. The following table presents the fair value and balance sheet classification of derivatives at March 31, 2018 and September 30, 2017 : Asset Derivatives Liability Derivatives March 31, 2018 September 30, 2017 March 31, 2018 September 30, 2017 Balance Sheet Balance Sheet Balance Sheet Balance Sheet Location Fair Value Location Fair Value Location Fair Value Location Fair Value (In thousands) Interest rate contracts Other assets $ 8,617 Other assets $ 1,139 Other liabilities $ 8,617 Other liabilities $ 1,139 Commercial loan hedges Other assets 2,217 Other assets — Other liabilities — Other liabilities 174 Borrowings hedges Other assets 15,328 Other assets — Other liabilities — Other liabilities 1,693 $ 26,162 $ 1,139 $ 8,617 $ 3,006

Income Taxes

Income Taxes	6 Months Ended
	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes On December 22, 2017, the U.S. Government enacted significant tax legislation commonly referred to as the Tax Cuts and Jobs Act (the “Tax Act”). For businesses, the Tax Act reduces the corporate federal tax rate from a maximum of 35% to a flat 21% rate. The corporate tax rate reduction was effective January 1, 2018. Because the Company has a fiscal year end of September 30, the reduced corporate tax rate will result in the application of a blended federal statutory tax rate of 24.53% for its fiscal year 2018 and then a flat 21% thereafter. Under generally accepted accounting principles, the Company uses the asset and liability method of accounting for income taxes. Under this method, deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. At September 30, 2017, the Company’s deferred tax assets and liabilities were determined based on the then-current enacted federal tax rate of 35% . As a result of the reduction in the corporate income tax rate under the Tax Act, the Company revalued its deferred tax assets and liabilities at December 31, 2017. Deferred tax assets and liabilities expected to be realized in fiscal year 2018 were re-measured using the aforementioned blended rate. All remaining deferred tax assets and liabilities were re-measured using the new statutory federal rate of 21% . These re-measurements resulted in a discrete tax benefit estimate of $3,743,000 that was recognized during the three months ended December 31, 2017. The Company’s revaluation of its deferred tax assets and liabilities is subject to further clarification of the Tax Act and refinements of its estimates.

Summary of Significant Accoun16

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Basis of Presentation	The Company has prepared the consolidated unaudited interim financial statements included in this report. All intercompany transactions and accounts have been eliminated in consolidation. The preparation of financial statements, in conformity with accounting principles generally accepted in the United States of America (“GAAP”), requires management to make estimates and assumptions that affect amounts reported in the financial statements. Actual results could differ from these estimates. In the opinion of management, all adjustments (consisting only of normal recurring adjustments) necessary for a fair presentation are reflected in the interim financial statements. Certain amounts in the financial statements from prior periods have been reclassified to conform to the current financial statement presentation. The information included in this Form 10-Q should be read in conjunction with the financial statements and related notes in the Company's 2017 Annual Report on Form 10-K (“ 2017 Annual Financial Statements”). Interim results are not necessarily indicative of results for a full year.
Off-Balance-Sheet Credit Exposures	The Company estimates losses on off-balance-sheet credit exposures by allocating a loss percentage derived from historical loss factors for each asset class.
New Accounting Pronouncements	In February 2018, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income . The ASU was issued to address certain stranded tax effects in accumulated other comprehensive income as a result of the Tax Cuts and Jobs Act of 2017. The guidance is effective for fiscal years beginning after December 15, 2018, including interim periods, therein, and early adoption is permitted. During the quarter ended March 31, 2018, the Company adopted the ASU and made a reclassification adjustment of $1,772,000 to increase accumulated other comprehensive income and decrease retained earnings on the Consolidated Statements of Changes in Stockholders' Equity. In August 2017, the FASB issued ASU 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities. The ASU expands and refines hedge accounting for both financial and non-financial risk components, aligns the recognition and presentation of the effects of hedging instruments and hedge items in the financial statements, and includes certain targeted improvements to ease the application of current guidance related to the assessment of hedge effectiveness. The effective date of the new standard for public companies is for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Early adoption is permitted. The new standard must be adopted using a modified retrospective transition with a cumulative effect adjustment recorded to opening retained earnings as of the initial adoption date. The Company does not anticipate that this guidance will have a material impact on its consolidated financial statements. In March 2017, the FASB issued ASU 2017-08, Receivables - Nonrefundable Fees and Other Costs (Subtopic 310-20), Premium Amortization on Purchased Callable Debt Securities. The ASU shortens the amortization period for certain callable debt securities held at a premium. Specifically, the amendments require the premium to be amortized to the earliest call date. The amendments do not require an accounting change for securities held at a discount; the discount continues to be amortized to maturity. The ASU is effective for public business entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. Early adoption is permitted, including adoption in an interim period. If an entity early adopts in an interim period, any adjustments should be reflected as of the beginning of the fiscal year that includes that interim period. The amendments should be applied on a modified retrospective basis, with a cumulative-effect adjustment directly to retained earnings as of the beginning of the period of adoption. The Company does not anticipate that this guidance will have a material impact on its consolidated financial statements . In February 2017, the FASB issued ASU 2017-05, Other Income - Gains and Losses from the Derecognition of Nonfinancial Assets (Subtopic 610-20): Clarifying the Scope of Asset Derecognition Guidance and Accounting for Partial Sales of Nonfinancial Assets. The ASU clarifies that a financial asset is within the scope of Subtopic 610-20 if it meets the definition of an in substance nonfinancial asset. The amendments also define the term in substance nonfinancial asset. The amendments clarify that nonfinancial assets within the scope of Subtopic 610-20 may include nonfinancial assets transferred within a legal entity to a counterparty. A contract that includes the transfer of ownership interests in one or more consolidated subsidiaries is within the scope of Subtopic 610-20 if substantially all of the fair value of the assets that are promised to the counterparty in a contract is concentrated in nonfinancial assets. The amendments clarify that an entity should identify each distinct nonfinancial asset or in substance nonfinancial asset promised to a counterparty and derecognize each asset when a counterparty obtains control of it. The ASU is effective for public business entities for annual periods beginning after December 15, 2017, and interim periods therein. Entities may use either a full or modified approach to adopt the ASU. The Company does not anticipate that this guidance will have a material impact on its consolidated financial statements. In January 2017, the FASB issued ASU 2017-04, Intangibles - Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment , which eliminates Step 2 from the goodwill impairment test. The ASU also eliminates the requirements for any reporting unit with a zero or negative carrying amount to perform a qualitative assessment and, if it fails that qualitative test, to perform Step 2 of the goodwill impairment test. An entity still has the option to perform the qualitative assessment for a reporting unit to determine if the quantitative impairment test is necessary. The ASU is effective for annual or interim goodwill impairment tests in fiscal years beginning after December 15, 2019, with early adoption being permitted for annual or interim goodwill impairment tests performed on testing dates after January 1, 2017. During the quarter ended March 31, 2018, the Company adopted the ASU and there was no impact on its consolidated financial statements. In January 2017, the FASB issued ASU 2017-01, Business Combinations Clarifying the Definition of a Business (Topic 805) , for determining whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The ASU is effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2017, with early adoption permitted for transactions that occurred before the issuance date or effective date of the standard if the transactions were not reported in financial statements that have been issued or made available for issuance. The ASU must be applied prospectively and upon adoption the standard will impact how we assess acquisitions (or disposals) of assets or businesses. During the quarter ended March 31, 2018, the Company adopted the ASU and there was no impact on its consolidated financial statements. In November 2016, the FASB issued ASU 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash: a Consensus of the FASB Emerging Issues Task Force . This ASU requires a company’s cash flow statement to explain the changes during a reporting period of the totals for cash, cash equivalents, restricted cash, and restricted cash equivalents. Additionally, amounts for restricted cash and restricted cash equivalents are to be included with cash and cash equivalents if the cash flow statement includes a reconciliation of the total cash balances for a reporting period. This ASU is effective for public business entities for annual periods, including interim periods within those annual periods, beginning after December 15, 2017, with early application permitted. The Company does not anticipate that this guidance will have a material impact on its consolidated financial statements. In August 2016, the FASB issued ASU 2016-15, Classification of Certain Cash Receipts and Cash Payments. The amendments in this ASU address eight specific cash flow issues with the objective of reducing diversity in practice. The specific issues identified include: debt prepayments or extinguishment costs; contingent consideration payments made after a business combination; proceeds from the settlement of insurance claims; proceeds from the settlement of corporate-owned life insurance policies (including bank-owned life insurance policies); distributions received from equity method investees; beneficial interests in securitization transactions; and separately identifiable cash flows and application of the predominance principle. This ASU is effective for fiscal years beginning after December 15, 2017, including interim periods within that reporting period; however, early adoption is permitted. The Company is currently evaluating the guidance to determine its adoption method and does not expect this guidance to have a material impact on its consolidated financial statements. In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses . The amendments in this ASU were issued to provide financial statement users with more decision-useful information about the expected credit losses on financial instruments that are not accounted for at fair value through net income, including loans held for investment, held-to-maturity debt securities, trade and other receivables, net investments in leases and other commitments to extend credit held by a reporting entity at each reporting date. The amendments require that financial assets measured at amortized cost be presented at the net amount expected to be collected, through an allowance for credit losses that is deducted from the amortized cost basis. The ASU eliminates the current framework of recognizing probable incurred losses and instead requires an entity to use its current estimate of all expected credit losses over the contractual life. The measurement of expected credit losses is based upon historical experience, current conditions, and reasonable and supportable forecasts that affect the collectability of the financial assets. For purchased financial assets with a more-than-insignificant amount of credit deterioration since origination (“PCD assets”) that are measured at amortized cost, an allowance for expected credit losses is recorded as an adjustment to the cost basis of the asset. Subsequent changes in estimated cash flows would be recorded as an adjustment to the allowance and through the statement of income. Credit losses relating to available-for-sale debt securities will be recorded through an allowance for credit losses rather than as a direct write-down to the security's cost basis. The amendments in this ASU are effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. For most debt securities, the transition approach requires a cumulative-effect adjustment to the statement of financial position as of the beginning of the first reporting period the guidance is effective. For other-than-temporarily impaired debt securities and PCD assets, the guidance will be applied prospectively. While the Company is currently in the process of evaluating the impact of the amended guidance on its consolidated financial statements, it currently expects the ALLL to increase upon adoption given that the allowance will be required to cover the full remaining expected life of the portfolio upon adoption, rather than the incurred loss model under current U.S. GAAP. The extent of this increase is still being evaluated and will depend on economic conditions and the composition of the Company’s loan and lease portfolio at the time of adoption. In February 2016, the FASB issued ASU 2016-02, Leases . The amendments require lessees to recognize a lease liability, which is a lessee's obligation to make lease payments arising from a lease, and a right-of-use asset, which is an asset that represents the lessee's right to use, or control the use of, a specified asset for the lease term. The guidance also simplifies the accounting for sale and leaseback transactions. The amendments are effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. Early application is permitted upon issuance. Lessees (for capital and operating leases) and lessors (for sales-type, direct financing, and operating leases) must apply a modified retrospective transition approach for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. The modified retrospective approach would not require any transition accounting for leases that expired before the earliest comparative period presented. Lessees and lessors may not apply a full retrospective transition approach. The Company is currently in the process of accumulating the lease data necessary to apply the amended guidance. The Company is continuing to evaluate the impact of the amended guidance on its consolidated financial statements, but the effects of recognizing most operating leases is not expected to be material. The Company expects to recognize right-of-use assets and lease liabilities for substantially all of its operating lease commitments based on the present value of unpaid lease payments as of the date of adoption. In January 2016, the FASB issued ASU 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities , to require all equity investments to be measured at fair value with changes in the fair value recognized through net income (other than those accounted for under equity method of accounting or those that result in consolidation of the investee). The amendments in this ASU also require an entity to present separately in other comprehensive income the portion of the total change in the fair value of a liability resulting from a change in the instrument-specific credit risk when the entity has elected to measure the liability at fair value in accordance with the fair value option for financial instruments. This ASU is effective for fiscal years beginning after December 15, 2017, including interim periods within that reporting period. The Company does not expect this guidance to have a material impact on its consolidated financial statements. In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606) . The guidance in this update supersedes the revenue recognition requirements in ASC Topic 605, Revenue Recognition, and most industry-specific guidance throughout the industry topics of the codification. For public companies, this update was to be effective for interim and annual periods beginning after December 15, 2016. However, in August 2015, the FASB issued ASU 2015-14, which delayed the effective date of ASU 2014-09 by one year and permits companies to voluntarily adopt the new standard as of the original effective date. The Company does not expect this guidance to have a material impact on its consolidated financial statements.

Loans Receivable (Tables)

Loans Receivable (Tables)	6 Months Ended
	Mar. 31, 2018
Receivables [Abstract]
Schedule of Loans Receivable	The following table is a summary of loans receivable. March 31, 2018 September 30, 2017 (In thousands) (In thousands) Gross loans by category Single-family residential $ 5,705,350 45.5 % $ 5,711,004 46.8 % Construction 1,732,202 13.8 1,597,996 13.1 Construction - custom 597,671 4.8 602,631 4.9 Land - acquisition & development 141,628 1.1 124,308 1.0 Land - consumer lot loans 102,779 0.8 104,405 0.9 Multi-family 1,328,049 10.6 1,303,148 10.7 Commercial real estate 1,443,437 11.5 1,434,610 11.8 Commercial & industrial 1,151,108 9.2 1,093,360 9.0 HELOC 135,119 1.1 144,850 1.2 Consumer 202,911 1.6 85,075 0.7 Total gross loans 12,540,254 100 % 12,201,387 100 % Less: Allowance for loan losses 127,576 123,073 Loans in process 1,141,018 1,149,934 Net deferred fees, costs and discounts 47,572 45,758 Total loan contra accounts 1,316,166 1,318,765 Net loans $ 11,224,088 $ 10,882,622
Summary of Information Regarding Non-Accrual Loans	The following table sets forth information regarding non-accrual loans. March 31, 2018 September 30, 2017 (In thousands) Non-accrual loans: Single-family residential $ 25,319 47.1 % $ 27,930 56.3 % Construction 2,296 4.3 — — Construction - custom — — 91 0.2 Land - acquisition & development 2,004 3.7 296 0.6 Land - consumer lot loans 1,045 1.9 605 1.2 Multi-family — — 139 0.3 Commercial real estate 9,527 17.7 11,815 23.8 Commercial & industrial 13,362 24.8 8,082 16.3 HELOC 217 0.4 531 1.1 Consumer 38 0.1 91 0.2 Total non-accrual loans $ 53,808 100 % $ 49,580 100 % % of total net loans 0.48 % 0.46 %
Analysis of Age of Loans in Past Due Status	The following tables provide details regarding delinquent loans. March 31, 2018 Loans Receivable Days Delinquent Based on $ Amount of Loans % based on $ Type of Loan Net of Loans In Process Current 30 60 90 Total Delinquent (In thousands) Single-family residential $ 5,704,505 $ 5,675,605 $ 6,268 $ 3,621 $ 19,011 $ 28,900 0.51 % Construction 916,662 913,419 948 — 2,295 3,243 0.35 Construction - custom 295,699 295,699 — — — — — Land - acquisition & development 119,063 117,200 — — 1,863 1,863 1.56 Land - consumer lot loans 102,705 101,837 328 — 540 868 0.85 Multi-family 1,328,027 1,327,864 29 134 — 163 0.01 Commercial real estate 1,443,437 1,441,459 1,275 98 605 1,978 0.14 Commercial & industrial 1,151,108 1,143,385 1,850 5,752 121 7,723 0.67 HELOC 135,119 134,866 163 30 60 253 0.19 Consumer 202,911 202,413 348 127 23 498 0.25 Total Loans $ 11,399,236 $ 11,353,747 $ 11,209 $ 9,762 $ 24,518 $ 45,489 0.40 % Delinquency % 99.60% 0.10% 0.09% 0.22% 0.40% September 30, 2017 Loans Receivable Days Delinquent Based on $ Amount of Loans % based on $ Type of Loan Net of Loans In Process Current 30 60 90 Total Delinquent (In thousands) Single-family residential $ 5,709,690 $ 5,671,933 $ 10,925 $ 4,810 $ 22,022 $ 37,757 0.66 % Construction 793,959 793,959 — — — — — Construction - custom 277,599 277,508 — — 91 91 0.03 Land - acquisition & development 104,856 104,526 — — 330 330 0.31 Land - consumer lot loans 104,335 103,389 112 680 154 946 0.91 Multi-family 1,303,119 1,302,720 5 255 139 399 0.03 Commercial real estate 1,434,610 1,432,052 507 — 2,051 2,558 0.18 Commercial & industrial 1,093,360 1,092,735 — 51 574 625 0.06 HELOC 144,850 143,974 221 342 313 876 0.60 Consumer 85,075 84,644 245 107 79 431 0.51 Total Loans $ 11,051,453 $ 11,007,440 $ 12,015 $ 6,245 $ 25,753 $ 44,013 0.40 % Delinquency % 99.60% 0.11% 0.06% 0.23% 0.40%
Schedule of Impaired Loans, Loan Commitments and Loans Serviced	The following table provides information related to loans that were restructured in a troubled debt restructuring ("TDR") during the periods presented: Three Months Ended March 31, 2018 2017 Pre-Modification Post-Modification Pre-Modification Post-Modification Outstanding Outstanding Outstanding Outstanding Number of Recorded Recorded Number of Recorded Recorded Contracts Investment Investment Contracts Investment Investment (In thousands) (In thousands) Troubled Debt Restructurings: Single-family residential 12 $ 2,183 $ 2,183 8 $ 1,712 $ 1,712 12 $ 2,183 $ 2,183 8 $ 1,712 $ 1,712 Six Months Ended March 31, 2018 2017 Pre-Modification Post-Modification Pre-Modification Post-Modification Outstanding Outstanding Outstanding Outstanding Number of Recorded Recorded Number of Recorded Recorded Contracts Investment Investment Contracts Investment Investment (In thousands) (In thousands) Troubled Debt Restructurings: Single-family residential 20 $ 4,195 $ 4,195 20 $ 3,846 $ 3,846 Land - consumer lot loans — — — 1 204 204 Commercial & Industrial 3 7,256 7,256 — — — HELOC — — — 1 228 228 23 $ 11,451 $ 11,451 22 $ 4,278 $ 4,278
Schedule of Loan Modifications	The following table provides information on payment defaults occurring during the periods presented where the loan had been modified in a TDR within 12 months of the payment default. Three Months Ended March 31, 2018 2017 Number of Recorded Number of Recorded Contracts Investment Contracts Investment (In thousands) (In thousands) Trouble Debt Restructurings That Subsequently Defaulted: Single-family residential 1 $ 162 7 $ 1,192 1 $ 162 7 $ 1,192 Six Months Ended March 31, 2018 2017 Number of Recorded Number of Recorded Contracts Investment Contracts Investment (In thousands) (In thousands) Troubled Debt Restructurings That Subsequently Defaulted: Single-family residential 2 $ 206 13 $ 3,185 Commercial real estate — — 2 267 2 $ 206 15 $ 3,452

Allowance for Losses on Loans (

Allowance for Losses on Loans (Tables)	6 Months Ended
	Mar. 31, 2018
Receivables [Abstract]
Summary of Activity in Allowance for Loan Losses	The following tables summarize the activity in the allowance for loan losses. Three Months Ended March 31, 2018 Beginning Allowance Charge-offs Recoveries Provision & Transfers Ending Allowance (In thousands) Single-family residential $ 35,928 $ (290 ) $ 211 $ (1,705 ) $ 34,144 Construction 25,214 — — 2,175 27,389 Construction - custom 2,052 — — 29 2,081 Land - acquisition & development 7,355 — 1,207 (940 ) 7,622 Land - consumer lot loans 2,906 (18 ) — (35 ) 2,853 Multi-family 7,904 — — 78 7,982 Commercial real estate 11,625 (36 ) 1 (2 ) 11,588 Commercial & industrial 29,268 — 115 (53 ) 29,330 HELOC 808 (1 ) — (5 ) 802 Consumer 4,095 (94 ) 276 (492 ) 3,785 $ 127,155 $ (439 ) $ 1,810 $ (950 ) $ 127,576 Three Months Ended March 31, 2017 Beginning Allowance Charge-offs Recoveries Provision & Transfers Ending Allowance (In thousands) Single-family residential $ 38,206 $ (381 ) $ 223 $ (884 ) $ 37,164 Construction 21,934 — — 3,127 25,061 Construction - custom 1,110 (3 ) — 69 1,176 Land - acquisition & development 6,665 (43 ) 4,211 (4,164 ) 6,669 Land - consumer lot loans 2,501 — 180 (168 ) 2,513 Multi-family 7,629 — — 300 7,929 Commercial real estate 10,168 — 1,164 (560 ) 10,772 Commercial & industrial 27,736 (105 ) 217 517 28,365 HELOC 832 (53 ) — 47 826 Consumer 1,675 (508 ) 314 (34 ) 1,447 $ 118,456 $ (1,093 ) $ 6,309 $ (1,750 ) $ 121,922 Six Months Ended March 31, 2018 Beginning Allowance Charge-offs Recoveries Provision & Transfers Ending Allowance (In thousands) Single-family residential $ 36,892 $ (750 ) $ 331 $ (2,329 ) $ 34,144 Construction 24,556 — — 2,833 27,389 Construction - custom 1,944 (50 ) — 187 2,081 Land - acquisition & development 6,829 — 4,579 (3,786 ) 7,622 Land - consumer lot loans 2,649 (66 ) — 270 2,853 Multi-family 7,862 — — 120 7,982 Commercial real estate 11,818 (36 ) 1 (195 ) 11,588 Commercial & industrial 28,524 (116 ) 170 752 29,330 HELOC 855 (1 ) 1 (53 ) 802 Consumer 1,144 (172 ) 562 2,251 3,785 $ 123,073 $ (1,191 ) $ 5,644 $ 50 $ 127,576 Six Months Ended March 31, 2017 Beginning Allowance Charge-offs Recoveries Provision & Transfers Ending Allowance (In thousands) Single-family residential $ 37,796 $ (496 ) $ 374 $ (510 ) $ 37,164 Construction 19,838 — — 5,223 25,061 Construction - custom 1,080 (3 ) — 99 1,176 Land - acquisition & development 6,023 (63 ) 8,229 (7,520 ) 6,669 Land - consumer lot loans 2,535 (17 ) 250 (255 ) 2,513 Multi-family 6,925 — — 1,004 7,929 Commercial real estate 8,588 (11 ) 1,520 675 10,772 Commercial & industrial 28,008 (163 ) 942 (422 ) 28,365 HELOC 813 (90 ) 1 102 826 Consumer 1,888 (654 ) 693 (480 ) 1,447 $ 113,494 $ (1,497 ) $ 12,009 $ (2,084 ) $ 121,922
Summary of Loans Collectively and Individually Evaluated for Impairment and Related Allocation of Reserves	The following tables show loans collectively and individually evaluated for impairment and the related allocation of general and specific reserves. March 31, 2018 Loans Collectively Evaluated for Impairment Loans Individually Evaluated for Impairment Allowance Allocation Recorded Investment of Loans Ratio Allowance Allocation Recorded Investment of Loans Ratio (In thousands) (In thousands) Single-family residential $ 34,144 $ 5,684,940 0.6 % $ — $ 27,608 — % Construction 27,389 911,650 3.0 — 5,012 — Construction - custom 2,081 295,699 0.7 — — — Land - acquisition & development 7,622 116,877 6.5 — 2,186 — Land - consumer lot loans 2,853 95,482 3.0 — 495 — Multi-family 7,978 1,324,959 0.6 4 3,068 0.1 Commercial real estate 11,484 1,385,851 0.8 104 39,861 0.3 Commercial & industrial 28,784 1,114,171 2.6 546 36,888 1.5 HELOC 802 133,152 0.6 — 273 — Consumer 3,785 202,766 1.9 — 38 — $ 126,922 $ 11,265,547 1.1 % $ 654 $ 115,429 0.6 % September 30, 2017 Loans Collectively Evaluated for Impairment Loans Individually Evaluated for Impairment Allowance Allocation Recorded Investment of Loans Ratio Allowance Allocation Recorded Investment of Loans Ratio (In thousands) (In thousands) Single-family residential $ 36,892 $ 5,713,576 0.7 % $ — $ 5,552 — % Construction 24,556 793,958 3.1 — — — Construction - custom 1,944 277,495 0.7 — 105 — Land - acquisition & development 6,828 104,767 6.5 1 89 1.0 Land - consumer lot loans 2,649 96,337 2.8 — 171 — Multi-family 7,857 1,302,625 0.6 5 493 1.0 Commercial real estate 11,698 1,391,668 0.8 120 21,765 0.6 Commercial & industrial 28,524 1,093,210 2.6 — 81 — HELOC 855 141,689 0.6 — 215 — Consumer 1,144 84,887 1.4 — 82 — $ 122,947 $ 11,000,212 1.1 % $ 126 $ 28,553 0.4 %
Summary of Loans Based on Credit Quality Indicators	The following tables provide information on loans based on risk rating categories as defined above. March 31, 2018 Internally Assigned Grade Pass Special mention Substandard Doubtful Loss Total Gross Loans (In thousands) Loan type Single-family residential $ 5,670,826 $ — $ 34,524 $ — $ — $ 5,705,350 Construction 1,727,190 — 5,012 — — 1,732,202 Construction - custom 597,671 — — — — 597,671 Land - acquisition & development 139,442 — 2,186 — — 141,628 Land - consumer lot loans 101,733 — 1,046 — — 102,779 Multi-family 1,325,076 379 2,594 — — 1,328,049 Commercial real estate 1,410,194 634 32,609 — — 1,443,437 Commercial & industrial 1,101,878 9,958 39,272 — — 1,151,108 HELOC 134,763 — 356 — — 135,119 Consumer 202,873 — 38 — — 202,911 Total gross loans $ 12,411,646 $ 10,971 $ 117,637 $ — $ — $ 12,540,254 Total grade as a % of total gross loans 99.0 % 0.1 % 0.9 % — % — % September 30, 2017 Internally Assigned Grade Pass Special mention Substandard Doubtful Loss Total Gross Loans (In thousands) Loan type Single-family residential $ 5,671,229 $ — $ 39,775 $ — $ — $ 5,711,004 Construction 1,594,926 — 3,070 — — 1,597,996 Construction - custom 602,540 — 91 — — 602,631 Land - acquisition & development 123,028 207 1,073 — — 124,308 Land - consumer lot loans 103,787 — 618 — — 104,405 Multi-family 1,295,261 5,795 2,092 — — 1,303,148 Commercial real estate 1,391,996 5,944 36,670 — — 1,434,610 Commercial & industrial 1,054,972 14,814 23,574 — — 1,093,360 HELOC 144,229 — 621 — — 144,850 Consumer 84,984 — 91 — — 85,075 Total gross loans $ 12,066,952 $ 26,760 $ 107,675 $ — $ — $ 12,201,387 Total grade as a % of total gross loans 98.9 % 0.2 % 0.9 % — % — % The following tables provide information on gross loans based on borrower payment activity. March 31, 2018 Performing Loans Non-Performing Loans Amount % of Total Gross Loans Amount % of Total Gross Loans (In thousands) Single-family residential $ 5,680,031 99.6 % $ 25,319 0.4 % Construction 1,729,906 99.9 2,296 0.1 Construction - custom 597,671 100.0 — — Land - acquisition & development 139,624 98.6 2,004 1.4 Land - consumer lot loans 101,734 99.0 1,045 1.0 Multi-family 1,328,049 100.0 — — Commercial real estate 1,433,910 99.3 9,527 0.7 Commercial & industrial 1,137,746 98.8 13,362 1.2 HELOC 134,902 99.8 217 0.2 Consumer 202,873 100.0 38 — $ 12,486,446 99.6 % $ 53,808 0.4 % September 30, 2017 Performing Loans Non-Performing Loans Amount % of Total Gross Loans Amount % of Total Gross Loans (In thousands) Single-family residential $ 5,683,074 99.5 % $ 27,930 0.5 % Construction 1,597,996 100.0 — — Construction - custom 602,540 99.9 91 0.1 Land - acquisition & development 124,012 99.8 296 0.2 Land - consumer lot loans 103,800 99.4 605 0.6 Multi-family 1,303,009 99.9 139 0.1 Commercial real estate 1,422,795 99.2 11,815 0.8 Commercial & industrial 1,085,278 99.3 8,082 0.7 HELOC 144,319 99.6 531 0.4 Consumer 84,984 99.9 91 0.1 $ 12,151,807 99.6 % $ 49,580 0.4 %
Summary of Impaired Loans Based on Type	The following tables provide information on impaired loan balances and the related allowances by loan types. March 31, 2018 Recorded Investment Unpaid Principal Balance Related Allowance Average Recorded Investment (Year-To-Date) (In thousands) Impaired loans with no related allowance recorded: Single-family residential $ 23,936 $ 25,229 $ — $ 21,889 Construction 5,898 5,898 — 2,289 Construction - custom — — — 49 Land - acquisition & development 2,186 2,230 — 1,297 Land - consumer lot loans 386 432 — 298 Multi-family 2,616 2,616 — 1,002 Commercial real estate 33,272 38,372 — 20,845 Commercial & industrial 29,882 29,989 — 14,200 HELOC 273 366 — 461 Consumer 38 104 — 65 98,487 105,236 — 62,395 Impaired loans with an allowance recorded: Single-family residential 162,875 166,405 2,942 171,831 Land - acquisition & development — — — 30 Land - consumer lot loans 6,837 7,431 — 7,397 Multi-family 473 473 4 482 Commercial real estate 11,818 12,673 104 12,936 Commercial & industrial 7,006 7,006 546 4,754 HELOC 1,424 1,506 — 1,503 Consumer 86 273 — 91 190,519 195,767 3,596 (1) 199,024 Total impaired loans: Single-family residential 186,811 191,634 2,942 193,720 Construction 5,898 5,898 — 2,289 Construction - custom — — — 49 Land - acquisition & development 2,186 2,230 — 1,327 Land - consumer lot loans 7,223 7,863 — 7,695 Multi-family 3,089 3,089 4 1,484 Commercial real estate 45,090 51,045 104 33,781 Commercial & industrial 36,888 36,995 546 18,954 HELOC 1,697 1,872 — 1,964 Consumer 124 377 — 156 $ 289,006 $ 301,003 $ 3,596 (1) $ 261,419 (1) Includes $654,000 of specific reserves and $2,942,000 included in the general reserves. September 30, 2017 Recorded Investment Unpaid Principal Balance Related Allowance Average Recorded Investment (In thousands) Impaired loans with no related allowance recorded: Single-family residential $ 21,325 $ 23,880 $ — $ 19,371 Construction - custom 148 165 — 231 Land - acquisition & development 330 8,208 — 176 Land - consumer lot loans 208 330 — 431 Multi-family 139 3,231 — 748 Commercial real estate 12,890 22,487 — 11,466 Commercial & industrial 8,279 14,321 — 7,425 HELOC 490 1,212 — 487 Consumer 88 1,433 — 57 43,897 75,267 — 40,392 Impaired loans with an allowance recorded: Single-family residential 181,941 186,167 4,030 204,723 Land - acquisition & development 90 90 1 576 Land - consumer lot loans 7,949 8,526 — 8,976 Multi-family 493 493 5 1,024 Commercial real estate 15,079 16,707 120 16,991 Commercial & industrial — — — 297 HELOC 1,728 1,806 — 1,451 Consumer 97 284 — 100 207,377 214,073 4,156 (1) 234,138 Total impaired loans: Single-family residential 203,266 210,047 4,030 224,094 Construction - custom 148 165 — 231 Land - acquisition & development 420 8,298 1 752 Land - consumer lot loans 8,157 8,856 — 9,407 Multi-family 632 3,724 5 1,772 Commercial real estate 27,969 39,194 120 28,457 Commercial & industrial 8,279 14,321 — 7,722 HELOC 2,218 3,018 — 1,938 Consumer 185 1,717 — 157 $ 251,274 $ 289,340 $ 4,156 (1) $ 274,530 (1) Includes $126,000 of specific reserves and $4,030,000 included in the general reserves

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value of Assets Measured on Recurring Basis	The following tables present the balance of assets and liabilities measured at fair value on a recurring basis. March 31, 2018 Level 1 Level 2 Level 3 Total (In thousands) Financial Assets Available-for-sale securities: Equity securities $ 495 $ — $ — $ 495 U.S. government and agency securities — 183,939 — 183,939 Municipal bonds — 26,196 — 26,196 Corporate debt securities — 183,457 — 183,457 Mortgage-backed securities Agency pass-through certificates — 866,822 — 866,822 Commercial MBS — 8,362 — 8,362 Total available-for-sale securities 495 1,268,776 — 1,269,271 Interest rate contracts — 8,617 — 8,617 Commercial loan hedges — 2,217 — 2,217 Borrowings hedges — 15,328 — 15,328 Total financial assets $ 495 $ 1,294,938 $ — $ 1,295,433 Financial Liabilities Interest rate contracts $ — $ 8,617 $ — $ 8,617 Total financial liabilities $ — $ 8,617 $ — $ 8,617 There were no transfers between, into and/or out of Levels 1, 2 or 3 during the six months ended March 31, 2018 . September 30, 2017 Level 1 Level 2 Level 3 Total (In thousands) Financial Assets Available-for-sale securities: Equity securities $ 522 $ — $ — $ 522 U.S. government and agency securities — 211,077 — 211,077 Municipal bonds — 26,624 — 26,624 Corporate debt securities — 185,298 — 185,298 Mortgage-backed securities Agency pass-through certificates — 834,297 — 834,297 Commercial MBS — 8,391 — 8,391 Total available-for-sale securities 522 1,265,687 — 1,266,209 Interest rate contracts — 1,139 — 1,139 Total financial assets $ 522 $ 1,266,826 $ — $ 1,267,348 Financial Liabilities Interest rate contracts $ — $ 1,139 $ — $ 1,139 Commercial loan hedges — 174 — 174 Borrowings hedges — 1,693 — 1,693 Total financial liabilities $ — $ 3,006 $ — $ 3,006
Aggregated Balance of Assets Measured at Estimated Fair Value on a Nonrecurring Basis and Total Losses Resulting from Those Fair Value Adjustments	The following tables present the aggregated balance of assets that were measured at fair value on a nonrecurring basis at March 31, 2018 and March 31, 2017 , and the total gains (losses) resulting from those fair value adjustments for the three and six months ended March 31, 2018 and March 31, 2017 . The estimated fair value measurements are shown gross of estimated selling costs. March 31, 2018 Three Months Ended March 31, 2018 Six Months Ended March 31, 2018 Level 1 Level 2 Level 3 Total Total Gains (Losses) (In thousands) Impaired loans (1) $ — $ — $ 7,343 $ 7,343 $ (466 ) $ (973 ) Real estate owned (2) — — 5,520 5,520 (379 ) (559 ) Balance at end of period $ — $ — $ 12,863 $ 12,863 $ (845 ) $ (1,532 ) (1) The gains (losses) represent remeasurements of collateral-dependent loans. (2) The gains (losses) represent aggregate writedowns and charge-offs on REO. March 31, 2017 Three Months Ended March 31, 2017 Six Months Ended March 31, 2017 Level 1 Level 2 Level 3 Total Total Gains (Losses) (In thousands) Impaired loans (1) $ — $ — $ 5,701 $ 5,701 $ (939 ) $ (1,361 ) Real estate owned (2) — — 5,822 5,822 (378 ) (619 ) Balance at end of period $ — $ — $ 11,523 $ 11,523 $ (1,317 ) $ (1,980 ) (1) The gains (losses) represent remeasurements of collateral-dependent loans. (2) The gains (losses) represent aggregate writedowns and charge-offs on REO.
Fair Value of Financial Instruments by Balance Sheet Grouping	Although management is not aware of any factors that would materially affect the estimated fair value amounts presented below, such amounts have not been comprehensively revalued for purposes of these financial statements since the dates shown, and therefore, estimates of fair value subsequent to those dates may differ significantly from the amounts presented below. March 31, 2018 September 30, 2017 Level in Fair Value Hierarchy Carrying Amount Estimated Fair Value Carrying Amount Estimated Fair Value (In thousands) Financial assets Cash and cash equivalents 1 $ 256,808 $ 256,808 $ 313,070 $ 313,070 Available-for-sale securities Equity securities 1 495 495 522 522 U.S. government and agency securities 2 183,939 183,939 211,077 211,077 Municipal bonds 2 26,196 26,196 26,624 26,624 Corporate debt securities 2 183,457 183,457 185,298 185,298 Mortgage-backed securities Agency pass-through certificates 2 866,822 866,822 834,297 834,297 Commercial MBS 2 8,362 8,362 8,391 8,391 Total available-for-sale securities 1,269,271 1,269,271 1,266,209 1,266,209 Held-to-maturity securities Mortgage-backed securities Agency pass-through certificates 2 1,701,566 1,652,787 1,646,856 1,635,913 Commercial MBS 2 15,000 15,000 — — Total held-to-maturity securities 1,716,566 1,667,787 1,646,856 1,635,913 Loans receivable 3 11,224,088 11,514,350 10,882,622 11,247,586 FDIC indemnification asset 3 — — 8,968 8,564 FHLB and FRB stock 2 126,990 126,990 122,990 122,990 Other assets - interest rate contracts 2 8,617 8,617 1,139 1,139 Other assets - commercial loan hedges 2 2,217 2,217 — — Other assets - borrowings hedges 2 15,328 15,328 — — Financial liabilities Customer accounts 2 11,138,856 10,627,045 10,835,008 10,411,686 FHLB advances 2 2,325,000 2,327,701 2,225,000 2,266,791 Other liabilities - interest rate contracts 2 8,617 8,617 1,139 1,139 Other liabilities - commercial loan hedges 2 — — 174 174 Other liabilities - borrowings hedges 2 — — 1,693 1,693 The following table presents the fair value and balance sheet classification of derivatives at March 31, 2018 and September 30, 2017 : Asset Derivatives Liability Derivatives March 31, 2018 September 30, 2017 March 31, 2018 September 30, 2017 Balance Sheet Balance Sheet Balance Sheet Balance Sheet Location Fair Value Location Fair Value Location Fair Value Location Fair Value (In thousands) Interest rate contracts Other assets $ 8,617 Other assets $ 1,139 Other liabilities $ 8,617 Other liabilities $ 1,139 Commercial loan hedges Other assets 2,217 Other assets — Other liabilities — Other liabilities 174 Borrowings hedges Other assets 15,328 Other assets — Other liabilities — Other liabilities 1,693 $ 26,162 $ 1,139 $ 8,617 $ 3,006
Reconciliation of Amortized Cost to Fair Value of Available-for-Sale and Held-to-Maturity Securities	The following tables provide a reconciliation of amortized cost to fair value of available-for-sale and held-to-maturity securities. March 31, 2018 Amortized Cost Gross Unrealized Fair Value Yield Gains Losses (In thousands) Available-for-sale securities U.S. government and agency securities due Within 1 year $ 3,300 $ 3 $ — $ 3,303 9.80 % 5 to 10 years 65,997 — (1,432 ) 64,565 2.33 Over 10 years 116,463 27 (419 ) 116,071 2.46 Equity securities due 1 to 5 years 500 — (5 ) 495 1.80 Corporate debt securities due 1 to 5 years 63,692 1,768 — 65,460 3.63 5 to 10 years 119,963 78 (2,044 ) 117,997 2.93 Municipal bonds due Within 1 year 2,359 — (2 ) 2,357 1.23 1 to 5 years 1,382 — (10 ) 1,372 2.05 Over 10 years 20,333 2,134 — 22,467 6.45 Mortgage-backed securities Agency pass-through certificates 870,741 3,400 (7,319 ) 866,822 3.24 Commercial MBS 8,350 12 — 8,362 3.85 1,273,080 7,422 (11,231 ) 1,269,271 3.18 Held-to-maturity securities Mortgage-backed securities Agency pass-through certificates 1,701,566 1,112 (49,891 ) 1,652,787 3.16 Commercial MBS 15,000 — — 15,000 2.66 1,716,566 1,112 (49,891 ) 1,667,787 3.16 $ 2,989,646 $ 8,534 $ (61,122 ) $ 2,937,058 3.17 % September 30, 2017 Amortized Cost Gross Unrealized Fair Value Yield Gains Losses (In thousands) Available-for-sale securities U.S. government and agency securities due Within 1 year $ 9,300 $ 146 $ — $ 9,446 10.38 % 1 to 5 years 5,688 2 — 5,690 1.51 5 to 10 years 69,108 — (1,238 ) 67,870 1.93 Over 10 years 127,936 353 (218 ) 128,071 1.92 Equity securities 1 to 5 years 500 22 — 522 1.80 Corporate bonds due 1 to 5 years 63,622 2,083 — 65,705 2.96 5 to 10 years 119,960 210 (577 ) 119,593 2.62 Municipal bonds due Within 1 year 2,344 10 — 2,354 1.23 1 to 5 years 1,367 55 — 1,422 2.05 Over 10 years 20,343 2,505 — 22,848 6.45 Mortgage-backed securities Agency pass-through certificates 828,069 8,402 (2,174 ) 834,297 2.96 Commercial MBS 8,350 41 — 8,391 3.31 1,256,587 13,829 (4,207 ) 1,266,209 2.86 Held-to-maturity securities Mortgage-backed securities Agency pass-through certificates 1,646,856 7,143 (18,086 ) 1,635,913 3.14 1,646,856 7,143 (18,086 ) 1,635,913 3.14 $ 2,903,443 $ 20,972 $ (22,293 ) $ 2,902,122 3.02 %
Schedule of Unrealized Losses and Fair Value of Securities	The following tables show the unrealized gross losses and fair value of securities as of March 31, 2018 and September 30, 2017 , by length of time that individual securities in each category have been in a continuous loss position. The decline in fair value since purchase is attributable to changes in interest rates. Because the Company does not intend to sell these securities and does not consider it more likely than not that it will be required to sell these securities before the recovery of amortized cost basis, which may be upon maturity, the Company does not consider these investments to be other than temporarily impaired. March 31, 2018 Less than 12 months 12 months or more Total Unrealized Gross Losses Fair Value Unrealized Gross Losses Fair Value Unrealized Gross Losses Fair Value (In thousands) Corporate debt securities $ — $ — $ (2,044 ) $ 97,956 $ (2,044 ) 97,956 Municipal bonds (12 ) 3,729 — — (12 ) 3,729 U.S. government and agency securities — — (1,851 ) 164,140 (1,851 ) 164,140 Equity securities (5 ) 495 — — (5 ) 495 Agency pass-through certificates (8,768 ) 583,301 (48,442 ) 1,428,150 (57,210 ) 2,011,451 $ (8,785 ) $ 587,525 $ (52,337 ) $ 1,690,246 $ (61,122 ) $ 2,277,771 September 30, 2017 Less than 12 months 12 months or more Total Unrealized Gross Losses Fair Value Unrealized Gross Losses Fair Value Unrealized Gross Losses Fair Value (In thousands) Corporate debt securities $ — $ — $ (577 ) $ 49,423 $ (577 ) $ 49,423 U.S. government and agency securities (759 ) 24,400 (697 ) 96,195 (1,456 ) 120,595 Agency pass-through certificates (17,683 ) 1,163,358 (2,577 ) 249,304 (20,260 ) 1,412,662 $ (18,442 ) $ 1,187,758 $ (3,851 ) $ 394,922 $ (22,293 ) $ 1,582,680

Derivatives and Hedging Activ20

Derivatives and Hedging Activities (Tables)	6 Months Ended
	Mar. 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Fair Value and Balance Sheet Classification	Although management is not aware of any factors that would materially affect the estimated fair value amounts presented below, such amounts have not been comprehensively revalued for purposes of these financial statements since the dates shown, and therefore, estimates of fair value subsequent to those dates may differ significantly from the amounts presented below. March 31, 2018 September 30, 2017 Level in Fair Value Hierarchy Carrying Amount Estimated Fair Value Carrying Amount Estimated Fair Value (In thousands) Financial assets Cash and cash equivalents 1 $ 256,808 $ 256,808 $ 313,070 $ 313,070 Available-for-sale securities Equity securities 1 495 495 522 522 U.S. government and agency securities 2 183,939 183,939 211,077 211,077 Municipal bonds 2 26,196 26,196 26,624 26,624 Corporate debt securities 2 183,457 183,457 185,298 185,298 Mortgage-backed securities Agency pass-through certificates 2 866,822 866,822 834,297 834,297 Commercial MBS 2 8,362 8,362 8,391 8,391 Total available-for-sale securities 1,269,271 1,269,271 1,266,209 1,266,209 Held-to-maturity securities Mortgage-backed securities Agency pass-through certificates 2 1,701,566 1,652,787 1,646,856 1,635,913 Commercial MBS 2 15,000 15,000 — — Total held-to-maturity securities 1,716,566 1,667,787 1,646,856 1,635,913 Loans receivable 3 11,224,088 11,514,350 10,882,622 11,247,586 FDIC indemnification asset 3 — — 8,968 8,564 FHLB and FRB stock 2 126,990 126,990 122,990 122,990 Other assets - interest rate contracts 2 8,617 8,617 1,139 1,139 Other assets - commercial loan hedges 2 2,217 2,217 — — Other assets - borrowings hedges 2 15,328 15,328 — — Financial liabilities Customer accounts 2 11,138,856 10,627,045 10,835,008 10,411,686 FHLB advances 2 2,325,000 2,327,701 2,225,000 2,266,791 Other liabilities - interest rate contracts 2 8,617 8,617 1,139 1,139 Other liabilities - commercial loan hedges 2 — — 174 174 Other liabilities - borrowings hedges 2 — — 1,693 1,693 The following table presents the fair value and balance sheet classification of derivatives at March 31, 2018 and September 30, 2017 : Asset Derivatives Liability Derivatives March 31, 2018 September 30, 2017 March 31, 2018 September 30, 2017 Balance Sheet Balance Sheet Balance Sheet Balance Sheet Location Fair Value Location Fair Value Location Fair Value Location Fair Value (In thousands) Interest rate contracts Other assets $ 8,617 Other assets $ 1,139 Other liabilities $ 8,617 Other liabilities $ 1,139 Commercial loan hedges Other assets 2,217 Other assets — Other liabilities — Other liabilities 174 Borrowings hedges Other assets 15,328 Other assets — Other liabilities — Other liabilities 1,693 $ 26,162 $ 1,139 $ 8,617 $ 3,006

Summary of Significant Accoun21

Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Sep. 30, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Goodwill	$ 301,368	$ 293,153
Other assets	187,193	185,826
Loans in process	1,141,018	1,149,934
Loans and Leases Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans in process	2,157,589	$ 1,992,905
Restatement Adjustment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Goodwill	7,135
Finite-lived intangible assets	5,106
Other assets	$ (12,241)

New Accounting Pronouncements (

New Accounting Pronouncements (Details) - Accounting Standards Update 2018-02 $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)
Accumulated Other Comprehensive Income (Loss)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification from AOCI to retained earnings	$ (1,772)
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification from AOCI to retained earnings	$ 1,772

Dividends and Share Repurchas23

Dividends and Share Repurchases (Details) - $ / shares	Apr. 30, 2018	Feb. 23, 2018	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Dividends Payable [Line Items]
Cash dividends per share (in dollars per share)		$ 0.17	$ 0.17	$ 0.4	$ 0.32	$ 0.54
Stock repurchased (in shares)			1,673,436
Average cost per share (in dollars per share)			$ 34.66
Warrants outstanding (in shares)			112,649		112,649
Remaining shares authorized to be repurchased (in shares)			4,080,149		4,080,149
2008 Troubled Asset Relief Program
Dividends Payable [Line Items]
Stock issued during period (in shares)			0
Subsequent Event
Dividends Payable [Line Items]
Dividends declared (in dollars per share)	$ 0.17

Loans Receivable - Schedule of

Loans Receivable - Schedule of Accounts, Notes, Loans, and Financing Receivable (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	$ 12,540,254		$ 12,201,387
Ratio of type of loan to total loans receivable	100.00%		100.00%
Allowance for loan losses	$ 127,576	$ 127,155	$ 123,073	$ 121,922	$ 118,456	$ 113,494
Loans in process	1,141,018		1,149,934
Net deferred fees, costs and discounts	47,572		45,758
Total loan contra accounts	1,316,166		1,318,765
Net loans	11,224,088		10,882,622
Single-family residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	$ 5,705,350		$ 5,711,004
Ratio of type of loan to total loans receivable	45.50%		46.80%
Allowance for loan losses	$ 34,144	35,928	$ 36,892	37,164	38,206	37,796
Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	$ 1,732,202		$ 1,597,996
Ratio of type of loan to total loans receivable	13.80%		13.10%
Allowance for loan losses	$ 27,389	25,214	$ 24,556	25,061	21,934	19,838
Construction - custom
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	$ 597,671		$ 602,631
Ratio of type of loan to total loans receivable	4.80%		4.90%
Allowance for loan losses	$ 2,081	2,052	$ 1,944	1,176	1,110	1,080
Land - acquisition & development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	$ 141,628		$ 124,308
Ratio of type of loan to total loans receivable	1.10%		1.00%
Allowance for loan losses	$ 7,622	7,355	$ 6,829	6,669	6,665	6,023
Land - consumer lot loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	$ 102,779		$ 104,405
Ratio of type of loan to total loans receivable	0.80%		0.90%
Allowance for loan losses	$ 2,853	2,906	$ 2,649	2,513	2,501	2,535
Multi-family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	$ 1,328,049		$ 1,303,148
Ratio of type of loan to total loans receivable	10.60%		10.70%
Allowance for loan losses	$ 7,982	7,904	$ 7,862	7,929	7,629	6,925
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	$ 1,443,437		$ 1,434,610
Ratio of type of loan to total loans receivable	11.50%		11.80%
Allowance for loan losses	$ 11,588	11,625	$ 11,818	10,772	10,168	8,588
Commercial & industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	$ 1,151,108		$ 1,093,360
Ratio of type of loan to total loans receivable	9.20%		9.00%
Allowance for loan losses	$ 29,330	29,268	$ 28,524	28,365	27,736	28,008
HELOC
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	$ 135,119		$ 144,850
Ratio of type of loan to total loans receivable	1.10%		1.20%
Allowance for loan losses	$ 802	808	$ 855	826	832	813
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	$ 202,911		$ 85,075
Ratio of type of loan to total loans receivable	1.60%		0.70%
Allowance for loan losses	$ 3,785	$ 4,095	$ 1,144	$ 1,447	$ 1,675	$ 1,888

Loans Receivable - Loans on No

Loans Receivable - Loans on Non-accrual Status (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Sep. 30, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual percent of total loans	0.48%	0.46%
Non-Accrual loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 53,808	$ 49,580
Ratio of nonaccrual loan by portfolio segment to total loans on nonaccrual status	100.00%	100.00%
Single-family residential | Non-Accrual loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 25,319	$ 27,930
Ratio of nonaccrual loan by portfolio segment to total loans on nonaccrual status	47.10%	56.30%
Construction | Non-Accrual loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 2,296	$ 0
Ratio of nonaccrual loan by portfolio segment to total loans on nonaccrual status	4.30%	0.00%
Construction - custom | Non-Accrual loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 0	$ 91
Ratio of nonaccrual loan by portfolio segment to total loans on nonaccrual status	0.00%	0.20%
Land - acquisition & development | Non-Accrual loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 2,004	$ 296
Ratio of nonaccrual loan by portfolio segment to total loans on nonaccrual status	3.70%	0.60%
Land - consumer lot loans | Non-Accrual loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 1,045	$ 605
Ratio of nonaccrual loan by portfolio segment to total loans on nonaccrual status	1.90%	1.20%
Multi-family | Non-Accrual loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 0	$ 139
Ratio of nonaccrual loan by portfolio segment to total loans on nonaccrual status	0.00%	0.30%
Commercial real estate | Non-Accrual loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 9,527	$ 11,815
Ratio of nonaccrual loan by portfolio segment to total loans on nonaccrual status	17.70%	23.80%
Commercial & industrial | Non-Accrual loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 13,362	$ 8,082
Ratio of nonaccrual loan by portfolio segment to total loans on nonaccrual status	24.80%	16.30%
HELOC | Non-Accrual loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 217	$ 531
Ratio of nonaccrual loan by portfolio segment to total loans on nonaccrual status	0.40%	1.10%
Consumer | Non-Accrual loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 38	$ 91
Ratio of nonaccrual loan by portfolio segment to total loans on nonaccrual status	0.10%	0.20%

Loans Receivable - Additional

Loans Receivable - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017	Sep. 30, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual interest income recognized			$ 3,228,000
Impaired, interest lost on nonaccrual loans			$ 1,073,000
Ratio of past due loans to total loans, net of charge-offs and LIPs	0.40%		0.40%		0.40%
Percent of TDRs classified as performing			97.70%
Troubled debt restructuring, amount	$ 2,183,000	$ 1,712,000	$ 11,451,000	$ 4,278,000
Basis point reduction, minimum			1.00%
Basis point reduction, maximum			2.00%
Single family residential loans as percentage of restructured loans	85.50%		85.50%
Covered assets	$ 54,626,000		$ 54,626,000		$ 67,914,000
Loans receivable, gross	12,540,254,000		12,540,254,000		12,201,387,000
FDIC indemnification asset	0		0		8,967,000
FDIC clawback liability	39,906,000		39,906,000		37,143,000
Covered loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	$ 50,777,000		$ 50,777,000		$ 61,810,000
Minimum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term for payment and rate reduction			6 months
Maximum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term for payment and rate reduction			24 months
Performing Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructuring, amount			$ 190,519,000

Loans Receivable - Loans Recei

Loans Receivable - Loans Receivable, Analysis of Age of Loans in Past Due Status (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Sep. 30, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount of loans, net of charge-offs and LIP	$ 11,399,236	$ 11,051,453
Current	11,353,747	11,007,440
Past due	$ 45,489	$ 44,013
Ratio of past due loans to total loans, net of charge-offs and LIPs	0.40%	0.40%
Ratio of total past due loans to total loans receivable, current	99.60%	99.60%
Ratio of total past due loans to total loans receivable, past due	0.40%	0.40%
30 Days Delinquent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	$ 11,209	$ 12,015
Ratio of total past due loans to total loans receivable, past due	0.10%	0.11%
60 Days Delinquent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	$ 9,762	$ 6,245
Ratio of total past due loans to total loans receivable, past due	0.09%	0.06%
90 Days Delinquent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	$ 24,518	$ 25,753
Ratio of total past due loans to total loans receivable, past due	0.22%	0.23%
Single-family residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount of loans, net of charge-offs and LIP	$ 5,704,505	$ 5,709,690
Current	5,675,605	5,671,933
Past due	$ 28,900	$ 37,757
Ratio of past due loans to total loans, net of charge-offs and LIPs	0.51%	0.66%
Single-family residential | 30 Days Delinquent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	$ 6,268	$ 10,925
Single-family residential | 60 Days Delinquent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	3,621	4,810
Single-family residential | 90 Days Delinquent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	19,011	22,022
Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount of loans, net of charge-offs and LIP	916,662	793,959
Current	913,419	793,959
Past due	$ 3,243	$ 0
Ratio of past due loans to total loans, net of charge-offs and LIPs	0.35%	0.00%
Construction | 30 Days Delinquent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	$ 948	$ 0
Construction | 60 Days Delinquent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	0	0
Construction | 90 Days Delinquent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	2,295	0
Construction - custom
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount of loans, net of charge-offs and LIP	295,699	277,599
Current	295,699	277,508
Past due	$ 0	$ 91
Ratio of past due loans to total loans, net of charge-offs and LIPs	0.00%	0.03%
Construction - custom | 30 Days Delinquent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	$ 0	$ 0
Construction - custom | 60 Days Delinquent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	0	0
Construction - custom | 90 Days Delinquent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	0	91
Land - acquisition & development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount of loans, net of charge-offs and LIP	119,063	104,856
Current	117,200	104,526
Past due	$ 1,863	$ 330
Ratio of past due loans to total loans, net of charge-offs and LIPs	1.56%	0.31%
Land - acquisition & development | 30 Days Delinquent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	$ 0	$ 0
Land - acquisition & development | 60 Days Delinquent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	0	0
Land - acquisition & development | 90 Days Delinquent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	1,863	330
Land - consumer lot loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount of loans, net of charge-offs and LIP	102,705	104,335
Current	101,837	103,389
Past due	$ 868	$ 946
Ratio of past due loans to total loans, net of charge-offs and LIPs	0.85%	0.91%
Land - consumer lot loans | 30 Days Delinquent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	$ 328	$ 112
Land - consumer lot loans | 60 Days Delinquent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	0	680
Land - consumer lot loans | 90 Days Delinquent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	540	154
Multi-family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount of loans, net of charge-offs and LIP	1,328,027	1,303,119
Current	1,327,864	1,302,720
Past due	$ 163	$ 399
Ratio of past due loans to total loans, net of charge-offs and LIPs	0.01%	0.03%
Multi-family | 30 Days Delinquent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	$ 29	$ 5
Multi-family | 60 Days Delinquent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	134	255
Multi-family | 90 Days Delinquent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	0	139
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount of loans, net of charge-offs and LIP	1,443,437	1,434,610
Current	1,441,459	1,432,052
Past due	$ 1,978	$ 2,558
Ratio of past due loans to total loans, net of charge-offs and LIPs	0.14%	0.18%
Commercial real estate | 30 Days Delinquent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	$ 1,275	$ 507
Commercial real estate | 60 Days Delinquent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	98	0
Commercial real estate | 90 Days Delinquent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	605	2,051
Commercial & industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount of loans, net of charge-offs and LIP	1,151,108	1,093,360
Current	1,143,385	1,092,735
Past due	$ 7,723	$ 625
Ratio of past due loans to total loans, net of charge-offs and LIPs	0.67%	0.06%
Commercial & industrial | 30 Days Delinquent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	$ 1,850	$ 0
Commercial & industrial | 60 Days Delinquent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	5,752	51
Commercial & industrial | 90 Days Delinquent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	121	574
HELOC
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount of loans, net of charge-offs and LIP	135,119	144,850
Current	134,866	143,974
Past due	$ 253	$ 876
Ratio of past due loans to total loans, net of charge-offs and LIPs	0.19%	0.60%
HELOC | 30 Days Delinquent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	$ 163	$ 221
HELOC | 60 Days Delinquent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	30	342
HELOC | 90 Days Delinquent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	60	313
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount of loans, net of charge-offs and LIP	202,911	85,075
Current	202,413	84,644
Past due	$ 498	$ 431
Ratio of past due loans to total loans, net of charge-offs and LIPs	0.25%	0.51%
Consumer | 30 Days Delinquent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	$ 348	$ 245
Consumer | 60 Days Delinquent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	127	107
Consumer | 90 Days Delinquent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	$ 23	$ 79

Loans Receivable - Troubled De

Loans Receivable - Troubled Debt Restructurings (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2018USD ($)contract	Mar. 31, 2017USD ($)contract	Mar. 31, 2018USD ($)contract	Mar. 31, 2017USD ($)contract
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of contracts | contract	12	8	23	22
Pre-modification outstanding recorded investment	$ 2,183	$ 1,712	$ 11,451	$ 4,278
Post-modification outstanding recorded investment	$ 2,183	$ 1,712	$ 11,451	$ 4,278
Single-family residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of contracts | contract	12	8	20	20
Pre-modification outstanding recorded investment	$ 2,183	$ 1,712	$ 4,195	$ 3,846
Post-modification outstanding recorded investment	$ 2,183	$ 1,712	$ 4,195	$ 3,846
Land - consumer lot loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of contracts | contract			0	1
Pre-modification outstanding recorded investment			$ 0	$ 204
Post-modification outstanding recorded investment			$ 0	$ 204
Commercial & industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of contracts | contract			3	0
Pre-modification outstanding recorded investment			$ 7,256	$ 0
Post-modification outstanding recorded investment			$ 7,256	$ 0
HELOC
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of contracts | contract			0	1
Pre-modification outstanding recorded investment			$ 0	$ 228
Post-modification outstanding recorded investment			$ 0	$ 228

Loans Receivable - Loan Modifi

Loans Receivable - Loan Modifications (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2018USD ($)contract	Mar. 31, 2017USD ($)contract	Mar. 31, 2018USD ($)contract	Mar. 31, 2017USD ($)contract
Financing Receivable, Modifications [Line Items]
Number of contracts | contract	1	7	2	15
Recorded investment | $	$ 162	$ 1,192	$ 206	$ 3,452
Single-family residential
Financing Receivable, Modifications [Line Items]
Number of contracts | contract	1	7	2	13
Recorded investment | $	$ 162	$ 1,192	$ 206	$ 3,185
Commercial real estate
Financing Receivable, Modifications [Line Items]
Number of contracts | contract			0	2
Recorded investment | $			$ 0	$ 267

Allowance for Losses on Loans

Allowance for Losses on Loans - Allowance for Credit Losses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Allowance	$ 127,155	$ 118,456	$ 123,073	$ 113,494
Charge-offs	(439)	(1,093)	(1,191)	(1,497)
Recoveries	1,810	6,309	5,644	12,009
Provision & Transfers	(950)	(1,750)	50	(2,084)
Ending Allowance	127,576	121,922	127,576	121,922
Single-family residential
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Allowance	35,928	38,206	36,892	37,796
Charge-offs	(290)	(381)	(750)	(496)
Recoveries	211	223	331	374
Provision & Transfers	(1,705)	(884)	(2,329)	(510)
Ending Allowance	34,144	37,164	34,144	37,164
Construction
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Allowance	25,214	21,934	24,556	19,838
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Provision & Transfers	2,175	3,127	2,833	5,223
Ending Allowance	27,389	25,061	27,389	25,061
Construction - custom
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Allowance	2,052	1,110	1,944	1,080
Charge-offs	0	(3)	(50)	(3)
Recoveries	0	0	0	0
Provision & Transfers	29	69	187	99
Ending Allowance	2,081	1,176	2,081	1,176
Land - acquisition & development
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Allowance	7,355	6,665	6,829	6,023
Charge-offs	0	(43)	0	(63)
Recoveries	1,207	4,211	4,579	8,229
Provision & Transfers	(940)	(4,164)	(3,786)	(7,520)
Ending Allowance	7,622	6,669	7,622	6,669
Land - consumer lot loans
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Allowance	2,906	2,501	2,649	2,535
Charge-offs	(18)	0	(66)	(17)
Recoveries	0	180	0	250
Provision & Transfers	(35)	(168)	270	(255)
Ending Allowance	2,853	2,513	2,853	2,513
Multi-family
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Allowance	7,904	7,629	7,862	6,925
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Provision & Transfers	78	300	120	1,004
Ending Allowance	7,982	7,929	7,982	7,929
Commercial real estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Allowance	11,625	10,168	11,818	8,588
Charge-offs	(36)	0	(36)	(11)
Recoveries	1	1,164	1	1,520
Provision & Transfers	(2)	(560)	(195)	675
Ending Allowance	11,588	10,772	11,588	10,772
Commercial & industrial
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Allowance	29,268	27,736	28,524	28,008
Charge-offs	0	(105)	(116)	(163)
Recoveries	115	217	170	942
Provision & Transfers	(53)	517	752	(422)
Ending Allowance	29,330	28,365	29,330	28,365
HELOC
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Allowance	808	832	855	813
Charge-offs	(1)	(53)	(1)	(90)
Recoveries	0	0	1	1
Provision & Transfers	(5)	47	(53)	102
Ending Allowance	802	826	802	826
Consumer
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Allowance	4,095	1,675	1,144	1,888
Charge-offs	(94)	(508)	(172)	(654)
Recoveries	276	314	562	693
Provision & Transfers	(492)	(34)	2,251	(480)
Ending Allowance	$ 3,785	$ 1,447	$ 3,785	$ 1,447

Allowance for Losses on Loans31

Allowance for Losses on Loans - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision (release) for loan losses	$ (950)	$ (1,600)	$ (950)	$ (1,600)
Charge-offs, net of (recoveries)	(1,371)	(5,216)	(4,453)	(10,512)
Loans receivable, gross	$ 12,540,254		$ 12,540,254			$ 12,201,387
Ratio of past due loans to total loans, net of charge-offs and LIPs	0.40%		0.40%			0.40%
Allowance for loan losses	$ 127,576	$ 121,922	$ 127,576	$ 121,922	$ 127,155	$ 123,073	$ 118,456	$ 113,494
Allowance for credit losses and reserve for unfunded commitments	$ 134,326		$ 134,326
Allowance for credit losses and reserve for unfunded commitments, percent of gross loans	1.07%		1.07%
Non-Accrual loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 53,808		$ 53,808			49,580
Loans Collectively Evaluated for Impairment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	11,265,547		11,265,547			11,000,212
Allowance for loan losses	126,922		126,922			122,947
Loans Individually Evaluated for Impairment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	115,429		115,429			28,553
Allowance for loan losses	654		654			126
Unfunded Loan Commitment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	6,750		6,750			7,750
Non-Performing Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	$ 69,712		$ 69,712			$ 70,238
Ratio of non-performing assets to total assets	0.45%		0.45%			0.46%
Nonaccrual loans	$ 53,808		$ 53,808			$ 49,580

Allowance for Losses on Loans32

Allowance for Losses on Loans - Loans Evaluated for Impairment (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	$ 127,576	$ 127,155	$ 123,073	$ 121,922	$ 118,456	$ 113,494
Loans receivable, gross	12,540,254		12,201,387
Loans Collectively Evaluated for Impairment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	126,922		122,947
Loans receivable, gross	$ 11,265,547		$ 11,000,212
Ratio	1.10%		1.10%
Loans Individually Evaluated for Impairment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	$ 654		$ 126
Loans receivable, gross	$ 115,429		$ 28,553
Ratio	0.60%		0.40%
Single-family residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	$ 34,144	35,928	$ 36,892	37,164	38,206	37,796
Loans receivable, gross	5,705,350		5,711,004
Single-family residential | Loans Collectively Evaluated for Impairment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	34,144		36,892
Loans receivable, gross	$ 5,684,940		$ 5,713,576
Ratio	0.60%		0.70%
Single-family residential | Loans Individually Evaluated for Impairment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	$ 0		$ 0
Loans receivable, gross	$ 27,608		$ 5,552
Ratio	0.00%		0.00%
Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	$ 27,389	25,214	$ 24,556	25,061	21,934	19,838
Loans receivable, gross	1,732,202		1,597,996
Construction | Loans Collectively Evaluated for Impairment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	27,389		24,556
Loans receivable, gross	$ 911,650		$ 793,958
Ratio	3.00%		3.10%
Construction | Loans Individually Evaluated for Impairment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	$ 0		$ 0
Loans receivable, gross	$ 5,012		$ 0
Ratio	0.00%		0.00%
Construction - custom
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	$ 2,081	2,052	$ 1,944	1,176	1,110	1,080
Loans receivable, gross	597,671		602,631
Construction - custom | Loans Collectively Evaluated for Impairment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	2,081		1,944
Loans receivable, gross	$ 295,699		$ 277,495
Ratio	0.70%		0.70%
Construction - custom | Loans Individually Evaluated for Impairment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	$ 0		$ 0
Loans receivable, gross	$ 0		$ 105
Ratio	0.00%		0.00%
Land - acquisition & development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	$ 7,622	7,355	$ 6,829	6,669	6,665	6,023
Loans receivable, gross	141,628		124,308
Land - acquisition & development | Loans Collectively Evaluated for Impairment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	7,622		6,828
Loans receivable, gross	$ 116,877		$ 104,767
Ratio	6.50%		6.50%
Land - acquisition & development | Loans Individually Evaluated for Impairment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	$ 0		$ 1
Loans receivable, gross	$ 2,186		$ 89
Ratio	0.00%		1.00%
Land - consumer lot loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	$ 2,853	2,906	$ 2,649	2,513	2,501	2,535
Loans receivable, gross	102,779		104,405
Land - consumer lot loans | Loans Collectively Evaluated for Impairment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	2,853		2,649
Loans receivable, gross	$ 95,482		$ 96,337
Ratio	3.00%		2.80%
Land - consumer lot loans | Loans Individually Evaluated for Impairment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	$ 0		$ 0
Loans receivable, gross	$ 495		$ 171
Ratio	0.00%		0.00%
Multi-family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	$ 7,982	7,904	$ 7,862	7,929	7,629	6,925
Loans receivable, gross	1,328,049		1,303,148
Multi-family | Loans Collectively Evaluated for Impairment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	7,978		7,857
Loans receivable, gross	$ 1,324,959		$ 1,302,625
Ratio	0.60%		0.60%
Multi-family | Loans Individually Evaluated for Impairment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	$ 4		$ 5
Loans receivable, gross	$ 3,068		$ 493
Ratio	0.10%		1.00%
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	$ 11,588	11,625	$ 11,818	10,772	10,168	8,588
Loans receivable, gross	1,443,437		1,434,610
Commercial real estate | Loans Collectively Evaluated for Impairment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	11,484		11,698
Loans receivable, gross	$ 1,385,851		$ 1,391,668
Ratio	0.80%		0.80%
Commercial real estate | Loans Individually Evaluated for Impairment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	$ 104		$ 120
Loans receivable, gross	$ 39,861		$ 21,765
Ratio	0.30%		0.60%
Commercial & industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	$ 29,330	29,268	$ 28,524	28,365	27,736	28,008
Loans receivable, gross	1,151,108		1,093,360
Commercial & industrial | Loans Collectively Evaluated for Impairment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	28,784		28,524
Loans receivable, gross	$ 1,114,171		$ 1,093,210
Ratio	2.60%		2.60%
Commercial & industrial | Loans Individually Evaluated for Impairment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	$ 546		$ 0
Loans receivable, gross	$ 36,888		$ 81
Ratio	1.50%		0.00%
HELOC
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	$ 802	808	$ 855	826	832	813
Loans receivable, gross	135,119		144,850
HELOC | Loans Collectively Evaluated for Impairment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	802		855
Loans receivable, gross	$ 133,152		$ 141,689
Ratio	0.60%		0.60%
HELOC | Loans Individually Evaluated for Impairment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	$ 0		$ 0
Loans receivable, gross	$ 273		$ 215
Ratio	0.00%		0.00%
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	$ 3,785	$ 4,095	$ 1,144	$ 1,447	$ 1,675	$ 1,888
Loans receivable, gross	202,911		85,075
Consumer | Loans Collectively Evaluated for Impairment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	3,785		1,144
Loans receivable, gross	$ 202,766		$ 84,887
Ratio	1.90%		1.40%
Consumer | Loans Individually Evaluated for Impairment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	$ 0		$ 0
Loans receivable, gross	$ 38		$ 82
Ratio	0.00%		0.00%

Allowance for Losses on Loans33

Allowance for Losses on Loans - Internally Assigned Grade (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Sep. 30, 2017
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	$ 12,540,254	$ 12,201,387
Pass
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	$ 12,411,646	$ 12,066,952
Total grade as a % of total net loans	99.00%	98.90%
Special mention
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	$ 10,971	$ 26,760
Total grade as a % of total net loans	0.10%	0.20%
Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	$ 117,637	$ 107,675
Total grade as a % of total net loans	0.90%	0.90%
Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	$ 0	$ 0
Total grade as a % of total net loans	0.00%	0.00%
Loss
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	$ 0	$ 0
Total grade as a % of total net loans	0.00%	0.00%
Single-family residential
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	$ 5,705,350	$ 5,711,004
Single-family residential | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	5,670,826	5,671,229
Single-family residential | Special mention
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	0	0
Single-family residential | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	34,524	39,775
Single-family residential | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	0	0
Single-family residential | Loss
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	0	0
Construction
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	1,732,202	1,597,996
Construction | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	1,727,190	1,594,926
Construction | Special mention
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	0	0
Construction | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	5,012	3,070
Construction | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	0	0
Construction | Loss
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	0	0
Construction - custom
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	597,671	602,631
Construction - custom | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	597,671	602,540
Construction - custom | Special mention
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	0	0
Construction - custom | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	0	91
Construction - custom | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	0	0
Construction - custom | Loss
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	0	0
Land - acquisition & development
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	141,628	124,308
Land - acquisition & development | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	139,442	123,028
Land - acquisition & development | Special mention
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	0	207
Land - acquisition & development | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	2,186	1,073
Land - acquisition & development | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	0	0
Land - acquisition & development | Loss
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	0	0
Land - consumer lot loans
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	102,779	104,405
Land - consumer lot loans | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	101,733	103,787
Land - consumer lot loans | Special mention
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	0	0
Land - consumer lot loans | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	1,046	618
Land - consumer lot loans | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	0	0
Land - consumer lot loans | Loss
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	0	0
Multi-family
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	1,328,049	1,303,148
Multi-family | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	1,325,076	1,295,261
Multi-family | Special mention
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	379	5,795
Multi-family | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	2,594	2,092
Multi-family | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	0	0
Multi-family | Loss
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	0	0
Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	1,443,437	1,434,610
Commercial real estate | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	1,410,194	1,391,996
Commercial real estate | Special mention
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	634	5,944
Commercial real estate | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	32,609	36,670
Commercial real estate | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	0	0
Commercial real estate | Loss
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	0	0
Commercial & industrial
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	1,151,108	1,093,360
Commercial & industrial | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	1,101,878	1,054,972
Commercial & industrial | Special mention
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	9,958	14,814
Commercial & industrial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	39,272	23,574
Commercial & industrial | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	0	0
Commercial & industrial | Loss
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	0	0
HELOC
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	135,119	144,850
HELOC | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	134,763	144,229
HELOC | Special mention
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	0	0
HELOC | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	356	621
HELOC | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	0	0
HELOC | Loss
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	0	0
Consumer
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	202,911	85,075
Consumer | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	202,873	84,984
Consumer | Special mention
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	0	0
Consumer | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	38	91
Consumer | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	0	0
Consumer | Loss
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	$ 0	$ 0

Allowance for Losses on Loans34

Allowance for Losses on Loans - Credit Risk Profile Based on Payment Activity (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Sep. 30, 2017
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	$ 12,540,254	$ 12,201,387
Performing Loans
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	$ 12,486,446	$ 12,151,807
Total grade as a % of total net loans	99.60%	99.60%
Non-Performing Loans
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	$ 69,712	$ 70,238
Nonaccrual loans by portfolio segment	$ 53,808	$ 49,580
Grade as a percentage of total gross loans	0.40%	0.40%
Single-family residential
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	$ 5,705,350	$ 5,711,004
Single-family residential | Performing Loans
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	$ 5,680,031	$ 5,683,074
Total grade as a % of total net loans	99.60%	99.50%
Single-family residential | Non-Performing Loans
Financing Receivable, Recorded Investment [Line Items]
Nonaccrual loans by portfolio segment	$ 25,319	$ 27,930
Grade as a percentage of total gross loans	0.40%	0.50%
Construction
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	$ 1,732,202	$ 1,597,996
Construction | Performing Loans
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	$ 1,729,906	$ 1,597,996
Total grade as a % of total net loans	99.90%	100.00%
Construction | Non-Performing Loans
Financing Receivable, Recorded Investment [Line Items]
Nonaccrual loans by portfolio segment	$ 2,296	$ 0
Grade as a percentage of total gross loans	0.10%	0.00%
Construction - custom
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	$ 597,671	$ 602,631
Construction - custom | Performing Loans
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	$ 597,671	$ 602,540
Total grade as a % of total net loans	100.00%	99.90%
Construction - custom | Non-Performing Loans
Financing Receivable, Recorded Investment [Line Items]
Nonaccrual loans by portfolio segment	$ 0	$ 91
Grade as a percentage of total gross loans	0.00%	0.10%
Land - acquisition & development
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	$ 141,628	$ 124,308
Land - acquisition & development | Performing Loans
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	$ 139,624	$ 124,012
Total grade as a % of total net loans	98.60%	99.80%
Land - acquisition & development | Non-Performing Loans
Financing Receivable, Recorded Investment [Line Items]
Nonaccrual loans by portfolio segment	$ 2,004	$ 296
Grade as a percentage of total gross loans	1.40%	0.20%
Land - consumer lot loans
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	$ 102,779	$ 104,405
Land - consumer lot loans | Performing Loans
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	$ 101,734	$ 103,800
Total grade as a % of total net loans	99.00%	99.40%
Land - consumer lot loans | Non-Performing Loans
Financing Receivable, Recorded Investment [Line Items]
Nonaccrual loans by portfolio segment	$ 1,045	$ 605
Grade as a percentage of total gross loans	1.00%	0.60%
Multi-family
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	$ 1,328,049	$ 1,303,148
Multi-family | Performing Loans
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	$ 1,328,049	$ 1,303,009
Total grade as a % of total net loans	100.00%	99.90%
Multi-family | Non-Performing Loans
Financing Receivable, Recorded Investment [Line Items]
Nonaccrual loans by portfolio segment	$ 0	$ 139
Grade as a percentage of total gross loans	0.00%	0.10%
Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	$ 1,443,437	$ 1,434,610
Commercial real estate | Performing Loans
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	$ 1,433,910	$ 1,422,795
Total grade as a % of total net loans	99.30%	99.20%
Commercial real estate | Non-Performing Loans
Financing Receivable, Recorded Investment [Line Items]
Nonaccrual loans by portfolio segment	$ 9,527	$ 11,815
Grade as a percentage of total gross loans	0.70%	0.80%
Commercial & industrial
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	$ 1,151,108	$ 1,093,360
Commercial & industrial | Performing Loans
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	$ 1,137,746	$ 1,085,278
Total grade as a % of total net loans	98.80%	99.30%
Commercial & industrial | Non-Performing Loans
Financing Receivable, Recorded Investment [Line Items]
Nonaccrual loans by portfolio segment	$ 13,362	$ 8,082
Grade as a percentage of total gross loans	1.20%	0.70%
HELOC
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	$ 135,119	$ 144,850
HELOC | Performing Loans
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	$ 134,902	$ 144,319
Total grade as a % of total net loans	99.80%	99.60%
HELOC | Non-Performing Loans
Financing Receivable, Recorded Investment [Line Items]
Nonaccrual loans by portfolio segment	$ 217	$ 531
Grade as a percentage of total gross loans	0.20%	0.40%
Consumer
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	$ 202,911	$ 85,075
Consumer | Performing Loans
Financing Receivable, Recorded Investment [Line Items]
Loans receivable, gross	$ 202,873	$ 84,984
Total grade as a % of total net loans	100.00%	99.90%
Consumer | Non-Performing Loans
Financing Receivable, Recorded Investment [Line Items]
Nonaccrual loans by portfolio segment	$ 38	$ 91
Grade as a percentage of total gross loans	0.00%	0.10%

Allowance for Losses on Loans35

Allowance for Losses on Loans - Impaired Loans Based on Loan Types (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Mar. 31, 2018	Sep. 30, 2017
Financing Receivable, Impaired [Line Items]
Recorded Investment	$ 289,006	$ 251,274
Unpaid Principal Balance	301,003	289,340
Related Allowance	3,596	4,156
Average Recorded Investment (Year-To-Date)	261,419	274,530
Amount of related allowance included in specific reserves	654	126
Amount of related allowance included in general reserves	2,942	4,030
Financing Receivable, Impairment, No Related Allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	98,487	43,897
Unpaid Principal Balance	105,236	75,267
Related Allowance	0	0
Average Recorded Investment (Year-To-Date)	62,395	40,392
Financing Receivable, Impairment, Allowance Recorded
Financing Receivable, Impaired [Line Items]
Recorded Investment	190,519	207,377
Unpaid Principal Balance	195,767	214,073
Related Allowance	3,596	4,156
Average Recorded Investment (Year-To-Date)	199,024	234,138
Single-family residential
Financing Receivable, Impaired [Line Items]
Recorded Investment	186,811	203,266
Unpaid Principal Balance	191,634	210,047
Related Allowance	2,942	4,030
Average Recorded Investment (Year-To-Date)	193,720	224,094
Single-family residential | Financing Receivable, Impairment, No Related Allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	23,936	21,325
Unpaid Principal Balance	25,229	23,880
Related Allowance	0	0
Average Recorded Investment (Year-To-Date)	21,889	19,371
Single-family residential | Financing Receivable, Impairment, Allowance Recorded
Financing Receivable, Impaired [Line Items]
Recorded Investment	162,875	181,941
Unpaid Principal Balance	166,405	186,167
Related Allowance	2,942	4,030
Average Recorded Investment (Year-To-Date)	171,831	204,723
Construction
Financing Receivable, Impaired [Line Items]
Recorded Investment	5,898
Unpaid Principal Balance	5,898
Related Allowance	0
Average Recorded Investment (Year-To-Date)	2,289
Construction | Financing Receivable, Impairment, No Related Allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	5,898
Unpaid Principal Balance	5,898
Related Allowance	0
Average Recorded Investment (Year-To-Date)	2,289
Construction, custom
Financing Receivable, Impaired [Line Items]
Recorded Investment	0	148
Unpaid Principal Balance	0	165
Related Allowance	0	0
Average Recorded Investment (Year-To-Date)	49	231
Construction, custom | Financing Receivable, Impairment, No Related Allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	0	148
Unpaid Principal Balance	0	165
Related Allowance	0	0
Average Recorded Investment (Year-To-Date)	49	231
Land - acquisition & development
Financing Receivable, Impaired [Line Items]
Recorded Investment	2,186	420
Unpaid Principal Balance	2,230	8,298
Related Allowance	0	1
Average Recorded Investment (Year-To-Date)	1,327	752
Land - acquisition & development | Financing Receivable, Impairment, No Related Allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	2,186	330
Unpaid Principal Balance	2,230	8,208
Related Allowance	0	0
Average Recorded Investment (Year-To-Date)	1,297	176
Land - acquisition & development | Financing Receivable, Impairment, Allowance Recorded
Financing Receivable, Impaired [Line Items]
Recorded Investment	0	90
Unpaid Principal Balance	0	90
Related Allowance	0	1
Average Recorded Investment (Year-To-Date)	30	576
Land - consumer lot loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	7,223	8,157
Unpaid Principal Balance	7,863	8,856
Related Allowance	0	0
Average Recorded Investment (Year-To-Date)	7,695	9,407
Land - consumer lot loans | Financing Receivable, Impairment, No Related Allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	386	208
Unpaid Principal Balance	432	330
Related Allowance	0	0
Average Recorded Investment (Year-To-Date)	298	431
Land - consumer lot loans | Financing Receivable, Impairment, Allowance Recorded
Financing Receivable, Impaired [Line Items]
Recorded Investment	6,837	7,949
Unpaid Principal Balance	7,431	8,526
Related Allowance	0	0
Average Recorded Investment (Year-To-Date)	7,397	8,976
Multi-family
Financing Receivable, Impaired [Line Items]
Recorded Investment	3,089	632
Unpaid Principal Balance	3,089	3,724
Related Allowance	4	5
Average Recorded Investment (Year-To-Date)	1,484	1,772
Multi-family | Financing Receivable, Impairment, No Related Allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	2,616	139
Unpaid Principal Balance	2,616	3,231
Related Allowance	0	0
Average Recorded Investment (Year-To-Date)	1,002	748
Multi-family | Financing Receivable, Impairment, Allowance Recorded
Financing Receivable, Impaired [Line Items]
Recorded Investment	473	493
Unpaid Principal Balance	473	493
Related Allowance	4	5
Average Recorded Investment (Year-To-Date)	482	1,024
Commercial real estate
Financing Receivable, Impaired [Line Items]
Recorded Investment	45,090	27,969
Unpaid Principal Balance	51,045	39,194
Related Allowance	104	120
Average Recorded Investment (Year-To-Date)	33,781	28,457
Commercial real estate | Financing Receivable, Impairment, No Related Allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	33,272	12,890
Unpaid Principal Balance	38,372	22,487
Related Allowance	0	0
Average Recorded Investment (Year-To-Date)	20,845	11,466
Commercial real estate | Financing Receivable, Impairment, Allowance Recorded
Financing Receivable, Impaired [Line Items]
Recorded Investment	11,818	15,079
Unpaid Principal Balance	12,673	16,707
Related Allowance	104	120
Average Recorded Investment (Year-To-Date)	12,936	16,991
Commercial & industrial
Financing Receivable, Impaired [Line Items]
Recorded Investment	36,888	8,279
Unpaid Principal Balance	36,995	14,321
Related Allowance	546	0
Average Recorded Investment (Year-To-Date)	18,954	7,722
Commercial & industrial | Financing Receivable, Impairment, No Related Allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	29,882	8,279
Unpaid Principal Balance	29,989	14,321
Related Allowance	0	0
Average Recorded Investment (Year-To-Date)	14,200	7,425
Commercial & industrial | Financing Receivable, Impairment, Allowance Recorded
Financing Receivable, Impaired [Line Items]
Recorded Investment	7,006	0
Unpaid Principal Balance	7,006	0
Related Allowance	546	0
Average Recorded Investment (Year-To-Date)	4,754	297
HELOC
Financing Receivable, Impaired [Line Items]
Recorded Investment	1,697	2,218
Unpaid Principal Balance	1,872	3,018
Related Allowance	0	0
Average Recorded Investment (Year-To-Date)	1,964	1,938
HELOC | Financing Receivable, Impairment, No Related Allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	273	490
Unpaid Principal Balance	366	1,212
Related Allowance	0	0
Average Recorded Investment (Year-To-Date)	461	487
HELOC | Financing Receivable, Impairment, Allowance Recorded
Financing Receivable, Impaired [Line Items]
Recorded Investment	1,424	1,728
Unpaid Principal Balance	1,506	1,806
Related Allowance	0	0
Average Recorded Investment (Year-To-Date)	1,503	1,451
Consumer
Financing Receivable, Impaired [Line Items]
Recorded Investment	124	185
Unpaid Principal Balance	377	1,717
Related Allowance	0	0
Average Recorded Investment (Year-To-Date)	156	157
Consumer | Financing Receivable, Impairment, No Related Allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	38	88
Unpaid Principal Balance	104	1,433
Related Allowance	0	0
Average Recorded Investment (Year-To-Date)	65	57
Consumer | Financing Receivable, Impairment, Allowance Recorded
Financing Receivable, Impaired [Line Items]
Recorded Investment	86	97
Unpaid Principal Balance	273	284
Related Allowance	0	0
Average Recorded Investment (Year-To-Date)	$ 91	$ 100

Fair Value Measurements - Recu

Fair Value Measurements - Recurring and Nonrecurring (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017	Sep. 30, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, at fair value	$ 1,269,271		$ 1,269,271		$ 1,266,209
Total financial assets	2,937,058		2,937,058		2,902,122
Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, at fair value	1,269,271		1,269,271		1,266,209
Total financial assets	1,295,433		1,295,433		1,267,348
Total financial liabilities	8,617		8,617		3,006
Recurring | Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	8,617		8,617		1,139
Derivative liabilities	8,617		8,617		1,139
Recurring | Commercial loan hedges
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	2,217		2,217
Derivative liabilities					174
Recurring | Borrowings hedges
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	15,328		15,328
Derivative liabilities					1,693
Recurring | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, at fair value	495		495		522
Recurring | U.S. government and agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, at fair value	183,939		183,939		211,077
Recurring | Municipal bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, at fair value	26,196		26,196		26,624
Recurring | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, at fair value	183,457		183,457		185,298
Recurring | Agency pass-through certificates
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, at fair value	866,822		866,822		834,297
Recurring | Commercial MBS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, at fair value	8,362		8,362		8,391
Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, at fair value	495		495		522
Total financial assets	495		495		522
Total financial liabilities	0		0		0
Recurring | Level 1 | Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0		0		0
Derivative liabilities	0		0		0
Recurring | Level 1 | Commercial loan hedges
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0		0
Derivative liabilities					0
Recurring | Level 1 | Borrowings hedges
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0		0
Derivative liabilities					0
Recurring | Level 1 | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, at fair value	495		495		522
Recurring | Level 1 | U.S. government and agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, at fair value	0		0		0
Recurring | Level 1 | Municipal bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, at fair value	0		0		0
Recurring | Level 1 | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, at fair value	0		0		0
Recurring | Level 1 | Agency pass-through certificates
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, at fair value	0		0		0
Recurring | Level 1 | Commercial MBS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, at fair value	0		0		0
Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, at fair value	1,268,776		1,268,776		1,265,687
Total financial assets	1,294,938		1,294,938		1,266,826
Total financial liabilities	8,617		8,617		3,006
Recurring | Level 2 | Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	8,617		8,617		1,139
Derivative liabilities	8,617		8,617		1,139
Recurring | Level 2 | Commercial loan hedges
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	2,217		2,217
Derivative liabilities					174
Recurring | Level 2 | Borrowings hedges
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	15,328		15,328
Derivative liabilities					1,693
Recurring | Level 2 | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, at fair value	0		0		0
Recurring | Level 2 | U.S. government and agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, at fair value	183,939		183,939		211,077
Recurring | Level 2 | Municipal bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, at fair value	26,196		26,196		26,624
Recurring | Level 2 | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, at fair value	183,457		183,457		185,298
Recurring | Level 2 | Agency pass-through certificates
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, at fair value	866,822		866,822		834,297
Recurring | Level 2 | Commercial MBS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, at fair value	8,362		8,362		8,391
Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, at fair value	0		0		0
Total financial assets	0		0		0
Total financial liabilities	0		0		0
Recurring | Level 3 | Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0		0		0
Derivative liabilities	0		0		0
Recurring | Level 3 | Commercial loan hedges
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0		0
Derivative liabilities					0
Recurring | Level 3 | Borrowings hedges
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0		0
Derivative liabilities					0
Recurring | Level 3 | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, at fair value	0		0		0
Recurring | Level 3 | U.S. government and agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, at fair value	0		0		0
Recurring | Level 3 | Municipal bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, at fair value	0		0		0
Recurring | Level 3 | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, at fair value	0		0		0
Recurring | Level 3 | Agency pass-through certificates
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, at fair value	0		0		0
Recurring | Level 3 | Commercial MBS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, at fair value	0		0		$ 0
Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, nonrecurring	12,863	$ 11,523	12,863	$ 11,523
Nonrecurring | Changes Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loss related to impaired loans and real estate held for sale, measured on nonrecurring basis	(845)	(1,317)	(1,532)	(1,980)
Nonrecurring | Impaired loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, nonrecurring	7,343	5,701	7,343	5,701
Nonrecurring | Impaired loans | Changes Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loss related to impaired loans and real estate held for sale, measured on nonrecurring basis	(466)	(939)	(973)	(1,361)
Nonrecurring | Real Estate Owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, nonrecurring	5,520	5,822	5,520	5,822
Nonrecurring | Real Estate Owned | Changes Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loss related to impaired loans and real estate held for sale, measured on nonrecurring basis	(379)	(378)	(559)	(619)
Nonrecurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, nonrecurring	0	0	0	0
Nonrecurring | Level 1 | Impaired loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, nonrecurring	0	0	0	0
Nonrecurring | Level 1 | Real Estate Owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, nonrecurring	0	0	0	0
Nonrecurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, nonrecurring	0	0	0	0
Nonrecurring | Level 2 | Impaired loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, nonrecurring	0	0	0	0
Nonrecurring | Level 2 | Real Estate Owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, nonrecurring	0	0	0	0
Nonrecurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, nonrecurring	12,863	11,523	12,863	11,523
Nonrecurring | Level 3 | Impaired loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, nonrecurring	7,343	5,701	7,343	5,701
Nonrecurring | Level 3 | Real Estate Owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, nonrecurring	$ 5,520	$ 5,822	$ 5,520	$ 5,822

Fair Value Measurements - Fair

Fair Value Measurements - Fair Value by Balance Sheet Grouping (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Sep. 30, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities	$ 1,269,271	$ 1,266,209
Held-to-maturity securities	1,667,787	1,635,913
FHLB and FRB stock	126,990	122,990
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities	1,269,271	1,266,209
Held-to-maturity securities	1,716,566	1,646,856
Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities	1,269,271	1,266,209
Held-to-maturity securities	1,667,787	1,635,913
Agency pass-through certificates
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity securities	1,652,787	1,635,913
Commercial MBS
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity securities	15,000
Level 1 | Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	256,808	313,070
Level 1 | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	256,808	313,070
Level 1 | Equity securities | Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities	495	522
Level 1 | Equity securities | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities	495	522
Level 2 | Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
FHLB and FRB stock	126,990	122,990
Customer accounts	11,138,856	10,835,008
FHLB advances	2,325,000	2,225,000
Level 2 | Carrying Amount | Interest rate contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other assets	8,617	1,139
Other liabilities	8,617	1,139
Level 2 | Carrying Amount | Commercial loan hedges
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other assets	2,217	0
Other liabilities	0	174
Level 2 | Carrying Amount | Borrowings hedges
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other assets	15,328	0
Other liabilities	0	1,693
Level 2 | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
FHLB and FRB stock	126,990	122,990
Customer accounts	10,627,045	10,411,686
FHLB advances	2,327,701	2,266,791
Level 2 | Estimated Fair Value | Interest rate contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other assets	8,617	1,139
Other liabilities	8,617	1,139
Level 2 | Estimated Fair Value | Commercial loan hedges
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other assets	2,217	0
Other liabilities	0	174
Level 2 | Estimated Fair Value | Borrowings hedges
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other assets	15,328	0
Other liabilities	0	1,693
Level 2 | Agency pass-through certificates | Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity securities	1,701,566	1,646,856
Level 2 | Agency pass-through certificates | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity securities	1,652,787	1,635,913
Level 2 | U.S. government and agency securities | Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities	183,939	211,077
Level 2 | U.S. government and agency securities | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities	183,939	211,077
Level 2 | Municipal bonds | Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities	26,196	26,624
Level 2 | Municipal bonds | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities	26,196	26,624
Level 2 | Corporate debt securities | Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities	183,457	185,298
Level 2 | Corporate debt securities | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities	183,457	185,298
Level 2 | Agency pass-through certificates | Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities	866,822	834,297
Level 2 | Agency pass-through certificates | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities	866,822	834,297
Level 2 | Commercial MBS | Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities	8,362	8,391
Held-to-maturity securities	15,000	0
Level 2 | Commercial MBS | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities	8,362	8,391
Held-to-maturity securities	15,000	0
Level 3 | Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans receivable	11,224,088	10,882,622
FDIC indemnification asset	0	8,968
Level 3 | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans receivable	11,514,350	11,247,586
FDIC indemnification asset	$ 0	$ 8,564

Fair Value Measurements - Inve

Fair Value Measurements - Investments by Contractual Maturity Date (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Sep. 30, 2017
Amortized Cost, Available-for-sale securities
Amortized Cost	$ 1,273,080	$ 1,256,587
Gross Unrealized Gains / Losses, Available-for-sale securities
Gross unrealized gains	7,422	13,829
Gross unrealized loss	11,231	4,207
Fair Value, Available-for-sale securities
Available-for-sale securities, at fair value	$ 1,269,271	$ 1,266,209
Yield, Available-for-sale securities
Yield	3.18%	2.86%
Amortized Cost, Held-to-maturity securities
Held-to-maturity securities, at amortized cost	$ 1,716,566	$ 1,646,856
Gross Unrealized Gains / Losses, Held-to-maturity securities
Held-to-maturity securities, Gross unrealized gains	1,112	7,143
Held-to-maturity securities ,Gross unrealized losses	(49,891)	(18,086)
Fair Value, Held-to-maturity securities
Held-to-maturity securities, Fair Value	$ 1,667,787	$ 1,635,913
Yield, Held-to-maturity securities
Held-to-maturity securities, Yield	3.16%	3.14%
Investments	$ 2,989,646	$ 2,903,443
Gross unrealized gains on investments	8,534	20,972
Gross unrealized losses on investments	(61,122)	(22,293)
Total financial assets	$ 2,937,058	$ 2,902,122
Yield on investments	3.17%	3.02%
U.S. government and agency securities
Amortized Cost, Available-for-sale securities
Within 1 year	$ 3,300	$ 9,300
1 to 5 years		5,688
5 to 10 years	65,997	69,108
Over 10 years	116,463	127,936
Gross Unrealized Gains / Losses, Available-for-sale securities
Gross unrealized gains, Within 1 year	3	146
Gross unrealized gains, 1 to 5 years		2
Gross unrealized gains, 5 to 10 years	0	0
Gross unrealized gains, Over 10 years	27	353
Gross unrealized losses, Within 1 year	0	0
Gross unrealized losses, 1 to 5 years		0
Gross unrealized losses, 5 to 10 years	(1,432)	(1,238)
Gross unrealized losses, Over 10 years	(419)	(218)
Fair Value, Available-for-sale securities
Within 1 year	3,303	9,446
1 to 5 years		5,690
5 to 10 years	64,565	67,870
Over 10 years	$ 116,071	$ 128,071
Yield, Available-for-sale securities
Within 1 year	9.80%	10.38%
1 to 5 years		1.51%
5 to 10 years	2.33%	1.93%
Over 10 years	2.46%	1.92%
Equity securities
Amortized Cost, Available-for-sale securities
1 to 5 years	$ 500	$ 500
Gross Unrealized Gains / Losses, Available-for-sale securities
Gross unrealized gains, 1 to 5 years	0	22
Gross unrealized losses, 1 to 5 years	(5)	0
Fair Value, Available-for-sale securities
1 to 5 years	$ 495	$ 522
Yield, Available-for-sale securities
1 to 5 years	1.80%	1.80%
Corporate debt securities
Amortized Cost, Available-for-sale securities
1 to 5 years	$ 63,692	$ 63,622
5 to 10 years	119,963	119,960
Gross Unrealized Gains / Losses, Available-for-sale securities
Gross unrealized gains, 1 to 5 years	1,768	2,083
Gross unrealized gains, 5 to 10 years	78	210
Gross unrealized losses, 1 to 5 years	0	0
Gross unrealized losses, 5 to 10 years	(2,044)	(577)
Fair Value, Available-for-sale securities
1 to 5 years	65,460	65,705
5 to 10 years	$ 117,997	$ 119,593
Yield, Available-for-sale securities
1 to 5 years	3.63%	2.96%
5 to 10 years	2.93%	2.62%
Municipal bonds
Amortized Cost, Available-for-sale securities
Within 1 year	$ 2,359	$ 2,344
1 to 5 years	1,382	1,367
Over 10 years	20,333	20,343
Gross Unrealized Gains / Losses, Available-for-sale securities
Gross unrealized gains, Within 1 year	0	10
Gross unrealized gains, 1 to 5 years	0	55
Gross unrealized gains, Over 10 years	2,134	2,505
Gross unrealized losses, Within 1 year	(2)	0
Gross unrealized losses, 1 to 5 years	(10)	0
Gross unrealized losses, Over 10 years	0	0
Fair Value, Available-for-sale securities
Within 1 year	2,357	2,354
1 to 5 years	1,372	1,422
Over 10 years	$ 22,467	$ 22,848
Yield, Available-for-sale securities
Within 1 year	1.23%	1.23%
1 to 5 years	2.05%	2.05%
Over 10 years	6.45%	6.45%
Agency pass-through certificates
Amortized Cost, Available-for-sale securities
Without single maturity date	$ 870,741	$ 828,069
Gross Unrealized Gains / Losses, Available-for-sale securities
Gross unrealized gains, Without single maturity date	3,400	8,402
Gross unrealized losses, Without single maturity date	(7,319)	(2,174)
Fair Value, Available-for-sale securities
Without single maturity date	$ 866,822	$ 834,297
Yield, Available-for-sale securities
Without single maturity date	3.24%	2.96%
Amortized Cost, Held-to-maturity securities
Held-to-maturity securities, at amortized cost	$ 1,701,566	$ 1,646,856
Gross Unrealized Gains / Losses, Held-to-maturity securities
Held-to-maturity securities, Gross unrealized gains	1,112	7,143
Held-to-maturity securities ,Gross unrealized losses	(49,891)	(18,086)
Fair Value, Held-to-maturity securities
Held-to-maturity securities, Fair Value	$ 1,652,787	$ 1,635,913
Yield, Held-to-maturity securities
Held-to-maturity securities, Yield	3.16%	3.14%
Commercial MBS
Amortized Cost, Available-for-sale securities
Without single maturity date	$ 8,350	$ 8,350
Gross Unrealized Gains / Losses, Available-for-sale securities
Gross unrealized gains, Without single maturity date	12	41
Gross unrealized losses, Without single maturity date	0	0
Fair Value, Available-for-sale securities
Without single maturity date	$ 8,362	$ 8,391
Yield, Available-for-sale securities
Without single maturity date	3.85%	3.31%
Amortized Cost, Held-to-maturity securities
Held-to-maturity securities, at amortized cost	$ 15,000
Gross Unrealized Gains / Losses, Held-to-maturity securities
Held-to-maturity securities, Gross unrealized gains	0
Held-to-maturity securities ,Gross unrealized losses	0
Fair Value, Held-to-maturity securities
Held-to-maturity securities, Fair Value	$ 15,000
Yield, Held-to-maturity securities
Held-to-maturity securities, Yield	2.66%

Fair Value Measurements - Addi

Fair Value Measurements - Additional Information (Details) - USD ($)	6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Fair Value Disclosures [Abstract]
Proceeds from sales of available-for-sale securities	$ 0	$ 350,890,000
Available-for-sale securities purchased	123,324,000	0
Held-to-maturity securities purchased	170,836,000	415,729,000
Proceeds from sale of held-to-maturity securities	$ 0	$ 0
Term of contractual due dates of substantially all mortgage-backed securities (in years)	10 years

Fair Value Measurements - Secu

Fair Value Measurements - Securities in Unrealized Loss Positions (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Sep. 30, 2017
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, unrealized gross losses	$ (8,785)	$ (18,442)
Less than 12 months, fair value	587,525	1,187,758
12 months or more, unrealized gross losses	(52,337)	(3,851)
12 months or more, fair value	1,690,246	394,922
Total unrealized gross losses	(61,122)	(22,293)
Total, fair value	2,277,771	1,582,680
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, unrealized gross losses	0	0
Less than 12 months, fair value	0	0
12 months or more, unrealized gross losses	(2,044)	(577)
12 months or more, fair value	97,956	49,423
Total unrealized gross losses	(2,044)	(577)
Total, fair value	97,956	49,423
Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, unrealized gross losses	(12)
Less than 12 months, fair value	3,729
12 months or more, unrealized gross losses	0
12 months or more, fair value	0
Total unrealized gross losses	(12)
Total, fair value	3,729
U.S. government and agency securities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, unrealized gross losses	0	(759)
Less than 12 months, fair value	0	24,400
12 months or more, unrealized gross losses	(1,851)	(697)
12 months or more, fair value	164,140	96,195
Total unrealized gross losses	(1,851)	(1,456)
Total, fair value	164,140	120,595
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, unrealized gross losses	(5)
Less than 12 months, fair value	495
12 months or more, unrealized gross losses	0
12 months or more, fair value	0
Total unrealized gross losses	(5)
Total, fair value	495
Agency pass-through certificates
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, unrealized gross losses	(8,768)	(17,683)
Less than 12 months, fair value	583,301	1,163,358
12 months or more, unrealized gross losses	(48,442)	(2,577)
12 months or more, fair value	1,428,150	249,304
Total unrealized gross losses	(57,210)	(20,260)
Total, fair value	$ 2,011,451	$ 1,412,662

Derivatives and Hedging Activ41

Derivatives and Hedging Activities (Details) - USD ($)	6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Sep. 30, 2017
Derivative [Line Items]
Gain (loss) on derivative instruments	$ 0	$ 0
Derivative asset, fair value	26,162,000		$ 1,139,000
Derivative liability, fair value	8,617,000		3,006,000
Interest rate swap agreements
Derivative [Line Items]
Customer derivatives program	808,981,000		1,035,573,000
Notional amount	700,000,000	$ 700,000,000
Commercial loan interest rate swap
Derivative [Line Items]
Notional amount	97,927,000		52,936,000
Interest rate contracts | Other assets
Derivative [Line Items]
Derivative asset, fair value	8,617,000		1,139,000
Interest rate contracts | Other liabilities
Derivative [Line Items]
Derivative liability, fair value	8,617,000		1,139,000
Commercial loan hedges | Other assets
Derivative [Line Items]
Derivative asset, fair value	2,217,000		0
Commercial loan hedges | Other liabilities
Derivative [Line Items]
Derivative liability, fair value	0		174,000
Borrowings hedges | Other assets
Derivative [Line Items]
Derivative asset, fair value	15,328,000		0
Borrowings hedges | Other liabilities
Derivative [Line Items]
Derivative liability, fair value	$ 0		$ 1,693,000

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Sep. 30, 2018
Income Tax Disclosures [Line Items]
Tax benefit from re-measurement of deferred tax assets and liabilities	$ 3,743
Scenario, Forecast
Income Tax Disclosures [Line Items]
Blended federal statutory tax rate		24.53%