Loans Receivable - Loans on Non-accrual Status (Details) - Non-Acquired loans - USD ($) $ in Thousands	Jun. 30, 2017	Sep. 30, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual of interest	$ 56,408	$ 42,414
Ratio of nonaccrual loan by portfolio segment to total loans on nonaccrual status	100.00%	100.00%
Single-family residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual of interest	$ 32,613	$ 33,148
Ratio of nonaccrual loan by portfolio segment to total loans on nonaccrual status	57.90%	78.20%
Construction - custom
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual of interest	$ 536	$ 0
Ratio of nonaccrual loan by portfolio segment to total loans on nonaccrual status	1.00%	0.00%
Land - acquisition & development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual of interest	$ 71	$ 58
Ratio of nonaccrual loan by portfolio segment to total loans on nonaccrual status	0.10%	0.10%
Land - consumer lot loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual of interest	$ 1,066	$ 510
Ratio of nonaccrual loan by portfolio segment to total loans on nonaccrual status	1.90%	1.20%
Multi-family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual of interest	$ 682	$ 776
Ratio of nonaccrual loan by portfolio segment to total loans on nonaccrual status	1.20%	1.80%
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual of interest	$ 12,983	$ 7,100
Ratio of nonaccrual loan by portfolio segment to total loans on nonaccrual status	23.00%	16.70%
Commercial & industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual of interest	$ 8,254	$ 583
Ratio of nonaccrual loan by portfolio segment to total loans on nonaccrual status	14.60%	1.40%
HELOC
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual of interest	$ 181	$ 239
Ratio of nonaccrual loan by portfolio segment to total loans on nonaccrual status	0.30%	0.60%
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual of interest	$ 22	$ 0
Ratio of nonaccrual loan by portfolio segment to total loans on nonaccrual status	0.00%	0.00%