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Allowance for Losses on Loans - Credit Risk Profile Based on Payment Activity (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Sep. 30, 2024
Financing Receivable, Credit Quality Indicator [Line Items]
Amount	$ 21,122,710	$ 21,120,107
Commercial loans
Financing Receivable, Credit Quality Indicator [Line Items]
Amount	12,238,959	12,205,420
Commercial loans | Multi-family
Financing Receivable, Credit Quality Indicator [Line Items]
Amount	4,867,340	4,556,200
Commercial loans | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Amount	3,639,477	3,732,155
Commercial loans | Commercial & industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Amount	2,384,745	2,332,732
Commercial loans | Construction
Financing Receivable, Credit Quality Indicator [Line Items]
Amount	1,211,336	1,424,016
Commercial loans | Land - acquisition & development
Financing Receivable, Credit Quality Indicator [Line Items]
Amount	136,061	160,317
Consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Amount	8,883,751	8,914,687
Consumer loans | Construction
Financing Receivable, Credit Quality Indicator [Line Items]
Amount	137,501	182,415
Consumer loans | Single-family residential
Financing Receivable, Credit Quality Indicator [Line Items]
Amount	8,264,318	8,280,300
Consumer loans | Land - consumer lot loans
Financing Receivable, Credit Quality Indicator [Line Items]
Amount	101,784	108,060
Consumer loans | HELOC
Financing Receivable, Credit Quality Indicator [Line Items]
Amount	288,228	269,857
Consumer loans | Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Amount	91,920	74,055
Performing Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Amount	$ 21,062,824	$ 21,050,566
% of Total Loans	99.70%	99.70%
Performing Loans | Commercial loans
Financing Receivable, Credit Quality Indicator [Line Items]
Amount	$ 12,199,162	$ 12,159,121
% of Total Loans	99.70%	99.60%
Performing Loans | Commercial loans | Multi-family
Financing Receivable, Credit Quality Indicator [Line Items]
Amount	$ 4,856,863	$ 4,537,457
% of Total Loans	99.80%	99.60%
Performing Loans | Commercial loans | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Amount	$ 3,610,157	$ 3,705,793
% of Total Loans	99.20%	99.30%
Performing Loans | Commercial loans | Commercial & industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Amount	$ 2,384,745	$ 2,332,732
% of Total Loans	100.00%	100.00%
Performing Loans | Commercial loans | Construction
Financing Receivable, Credit Quality Indicator [Line Items]
Amount	$ 1,211,336	$ 1,422,896
% of Total Loans	100.00%	99.90%
Performing Loans | Commercial loans | Land - acquisition & development
Financing Receivable, Credit Quality Indicator [Line Items]
Amount	$ 136,061	$ 160,243
% of Total Loans	100.00%	100.00%
Performing Loans | Consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Amount	$ 8,863,662	$ 8,891,445
% of Total Loans	99.80%	99.70%
Performing Loans | Consumer loans | Construction
Financing Receivable, Credit Quality Indicator [Line Items]
Amount	$ 136,654	$ 181,567
% of Total Loans	99.40%	99.50%
Performing Loans | Consumer loans | Single-family residential
Financing Receivable, Credit Quality Indicator [Line Items]
Amount	$ 8,245,584	$ 8,258,812
% of Total Loans	99.80%	99.70%
Performing Loans | Consumer loans | Land - consumer lot loans
Financing Receivable, Credit Quality Indicator [Line Items]
Amount	$ 101,776	$ 108,060
% of Total Loans	100.00%	100.00%
Performing Loans | Consumer loans | HELOC
Financing Receivable, Credit Quality Indicator [Line Items]
Amount	$ 287,928	$ 269,261
% of Total Loans	99.90%	99.80%
Performing Loans | Consumer loans | Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Amount	$ 91,720	$ 73,745
% of Total Loans	99.80%	99.60%
Non-Performing Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Amount	$ 59,886	$ 69,541
% of Total Loans	0.30%	0.30%
Non-Performing Loans | Commercial loans
Financing Receivable, Credit Quality Indicator [Line Items]
Amount	$ 39,797	$ 46,299
% of Total Loans	0.30%	0.40%
Non-Performing Loans | Commercial loans | Multi-family
Financing Receivable, Credit Quality Indicator [Line Items]
Amount	$ 10,477	$ 18,743
% of Total Loans	0.20%	0.40%
Non-Performing Loans | Commercial loans | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Amount	$ 29,320	$ 26,362
% of Total Loans	0.80%	0.70%
Non-Performing Loans | Commercial loans | Commercial & industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Amount	$ 0	$ 0
% of Total Loans	0.00%	0.00%
Non-Performing Loans | Commercial loans | Construction
Financing Receivable, Credit Quality Indicator [Line Items]
Amount	$ 0	$ 1,120
% of Total Loans	0.00%	0.10%
Non-Performing Loans | Commercial loans | Land - acquisition & development
Financing Receivable, Credit Quality Indicator [Line Items]
Amount	$ 0	$ 74
% of Total Loans	0.00%	0.00%
Non-Performing Loans | Consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Amount	$ 20,089	$ 23,242
% of Total Loans	0.20%	0.30%
Non-Performing Loans | Consumer loans | Construction
Financing Receivable, Credit Quality Indicator [Line Items]
Amount	$ 847	$ 848
% of Total Loans	0.60%	0.50%
Non-Performing Loans | Consumer loans | Single-family residential
Financing Receivable, Credit Quality Indicator [Line Items]
Amount	$ 18,734	$ 21,488
% of Total Loans	0.20%	0.30%
Non-Performing Loans | Consumer loans | Land - consumer lot loans
Financing Receivable, Credit Quality Indicator [Line Items]
Amount	$ 8	$ 0
% of Total Loans	0.00%	0.00%
Non-Performing Loans | Consumer loans | HELOC
Financing Receivable, Credit Quality Indicator [Line Items]
Amount	$ 300	$ 596
% of Total Loans	0.10%	0.20%
Non-Performing Loans | Consumer loans | Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Amount	$ 200	$ 310
% of Total Loans	0.20%	0.40%

X

- Definition

Amortized cost excluding accrued interest, before allowance for credit loss, of financing receivable. Excludes net investment in lease.

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No definition available.

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