Allowance for Losses on Loans - Allowance for Credit Losses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Allowance	$ 109,919	$ 108,323	$ 106,829	$ 114,591
Charge-offs	(1,175)	(6,551)	(5,234)	(11,677)
Recoveries	4,072	6,238	12,722	15,329
Provision & Transfers	(1,800)	(2,399)	(3,301)	(12,632)
Ending Allowance	111,016	105,611	111,016	105,611
Single-family residential
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Allowance	41,828	54,762	47,347	62,763
Charge-offs	(634)	(1,698)	(2,800)	(4,801)
Recoveries	162	3,878	2,739	10,553
Provision & Transfers	(675)	(4,938)	(6,605)	(16,511)
Ending Allowance	40,681	52,004	40,681	52,004
Construction
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Allowance	15,726	5,445	6,680	6,742
Charge-offs	0	0	0	(388)
Recoveries	207	0	357	75
Provision & Transfers	1,729	488	10,625	(496)
Ending Allowance	17,662	5,933	17,662	5,933
Construction - custom
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Allowance	1,022	968	990	1,695
Charge-offs	0	0	(60)	0
Recoveries	60	0	60	0
Provision & Transfers	(54)	17	38	(710)
Ending Allowance	1,028	985	1,028	985
Land - acquisition & development
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Allowance	7,252	7,405	5,781	5,592
Charge-offs	(31)	0	(31)	(38)
Recoveries	2,741	1	6,148	206
Provision & Transfers	(3,240)	(1,634)	(5,176)	12
Ending Allowance	6,722	5,772	6,722	5,772
Land - consumer lot loans
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Allowance	2,466	3,035	2,946	3,077
Charge-offs	(26)	(276)	(701)	(363)
Recoveries	5	187	5	221
Provision & Transfers	59	53	254	64
Ending Allowance	2,504	2,999	2,504	2,999
Multi-family
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Allowance	6,784	4,673	5,304	4,248
Charge-offs	0	0	0	0
Recoveries	0	0	0	220
Provision & Transfers	137	362	1,617	567
Ending Allowance	6,921	5,035	6,921	5,035
Commercial real estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Allowance	7,783	6,734	8,960	7,548
Charge-offs	0	(1,592)	(32)	(1,619)
Recoveries	454	230	1,569	711
Provision & Transfers	(94)	1,896	(2,354)	628
Ending Allowance	8,143	7,268	8,143	7,268
Commercial & industrial
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Allowance	23,824	21,146	24,980	16,527
Charge-offs	(150)	(2,106)	(729)	(2,461)
Recoveries	6	896	597	948
Provision & Transfers	716	1,726	(452)	6,648
Ending Allowance	24,396	21,662	24,396	21,662
HELOC
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Allowance	828	850	902	928
Charge-offs	(27)	(26)	(54)	(26)
Recoveries	0	1	21	1
Provision & Transfers	55	39	(13)	(39)
Ending Allowance	856	864	856	864
Consumer
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Allowance	2,406	3,305	2,939	3,227
Charge-offs	(307)	(853)	(827)	(1,981)
Recoveries	437	1,045	1,226	2,394
Provision & Transfers	(433)	(408)	(1,235)	(551)
Ending Allowance	$ 2,103	3,089	$ 2,103	3,089
Covered loans
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Allowance				2,244
Provision & Transfers				(2,244)
Ending Allowance		$ 0		$ 0