Loans Receivable (excluding Covered Loans) (Details) (USD $)	3 Months Ended	12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Sep. 30, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	$ 8,031,093,000	$ 7,866,336,000
Ratio of type of loan to total loans receivable	100.00%	100.00%
Allowance for probable losses	126,827,000	133,147,000	157,160,000
Loans in process	204,566,000	213,286,000
Discount on acquired loans	50,817,000	33,484,000
Deferred net origination fees	33,973,000	34,421,000
Charges against loans receivable	416,183,000	414,338,000
Loans receivable, net	7,614,910,000	7,451,998,000
Residential Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	5,589,425,000	5,779,264,000
Ratio of type of loan to total loans receivable	69.60%	73.50%
Allowance for probable losses	77,508,000	81,815,000	83,307,000
Construction, Speculative [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	125,716,000	131,526,000
Ratio of type of loan to total loans receivable	1.50%	1.60%
Allowance for probable losses	8,660,000	12,060,000	13,828,000
Construction, Custom [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	229,134,000	211,690,000
Ratio of type of loan to total loans receivable	2.90%	2.70%
Allowance for probable losses	275,000	347,000	623,000
Land, Acquisition and Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	115,655,000	128,379,000
Ratio of type of loan to total loans receivable	1.40%	1.70%
Allowance for probable losses	15,056,000	15,598,000	32,719,000
Land, Consumer Lot Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	140,997,000	141,844,000
Ratio of type of loan to total loans receivable	1.80%	1.80%
Allowance for probable losses	4,963,000	4,937,000	5,520,000
Multi Family Housing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	731,135,000	710,741,000
Ratio of type of loan to total loans receivable	9.20%	9.00%
Allowance for probable losses	5,107,000	5,280,000	7,623,000
Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	609,948,000	406,364,000
Ratio of type of loan to total loans receivable	7.60%	5.20%
Allowance for probable losses	2,651,000	1,956,000	4,331,000
Commercial and Industrial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	280,458,000	166,115,000
Ratio of type of loan to total loans receivable	3.40%	2.10%
Allowance for probable losses	8,062,000	7,626,000	5,099,000
Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	138,645,000	126,942,000
Ratio of type of loan to total loans receivable	1.80%	1.60%
Allowance for probable losses	1,044,000	965,000	1,139,000
Consumer Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	69,980,000	63,471,000
Ratio of type of loan to total loans receivable	0.80%	0.80%
Allowance for probable losses	3,501,000	2,563,000	2,971,000
Non-Acquired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	7,584,292,000	7,755,219,000
Ratio of type of loan to total loans receivable	94.40%	98.60%
Non-Acquired Loans [Member] | Residential Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	5,573,590,000	5,778,922,000
Ratio of type of loan to total loans receivable	69.40%	73.50%
Non-Acquired Loans [Member] | Construction, Speculative [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	123,871,000	129,637,000
Ratio of type of loan to total loans receivable	1.50%	1.60%
Non-Acquired Loans [Member] | Construction, Custom [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	228,140,000	211,690,000
Ratio of type of loan to total loans receivable	2.90%	2.70%
Non-Acquired Loans [Member] | Land, Acquisition and Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	109,458,000	124,677,000
Ratio of type of loan to total loans receivable	1.40%	1.60%
Non-Acquired Loans [Member] | Land, Consumer Lot Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	137,106,000	141,844,000
Ratio of type of loan to total loans receivable	1.70%	1.80%
Non-Acquired Loans [Member] | Multi Family Housing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	721,802,000	710,140,000
Ratio of type of loan to total loans receivable	9.00%	9.00%
Non-Acquired Loans [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	347,564,000	319,210,000
Ratio of type of loan to total loans receivable	4.30%	4.10%
Non-Acquired Loans [Member] | Commercial and Industrial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	171,644,000	162,823,000
Ratio of type of loan to total loans receivable	2.10%	2.10%
Non-Acquired Loans [Member] | Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	111,986,000	112,902,000
Ratio of type of loan to total loans receivable	1.40%	1.40%
Non-Acquired Loans [Member] | Consumer Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	59,131,000	63,374,000
Ratio of type of loan to total loans receivable	0.70%	0.80%
Acquired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	343,550,000	0
Ratio of type of loan to total loans receivable	4.30%	0.00%
Acquired Loans [Member] | Residential Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	15,495,000	0
Ratio of type of loan to total loans receivable	0.20%	0.00%
Acquired Loans [Member] | Construction, Speculative [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	90,000	0
Ratio of type of loan to total loans receivable	0.00%	0.00%
Acquired Loans [Member] | Construction, Custom [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	994,000	0
Ratio of type of loan to total loans receivable	0.00%	0.00%
Acquired Loans [Member] | Land, Acquisition and Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	3,520,000	0
Ratio of type of loan to total loans receivable	0.00%	0.00%
Acquired Loans [Member] | Land, Consumer Lot Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	3,891,000	0
Ratio of type of loan to total loans receivable	0.10%	0.00%
Acquired Loans [Member] | Multi Family Housing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	9,333,000	0
Ratio of type of loan to total loans receivable	0.20%	0.00%
Acquired Loans [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	178,727,000	0
Ratio of type of loan to total loans receivable	2.20%	0.00%
Acquired Loans [Member] | Commercial and Industrial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	106,931,000	0
Ratio of type of loan to total loans receivable	1.30%	0.00%
Acquired Loans [Member] | Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	13,810,000	0
Ratio of type of loan to total loans receivable	0.20%	0.00%
Acquired Loans [Member] | Consumer Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	10,759,000	0
Ratio of type of loan to total loans receivable	0.10%	0.00%
Credit Impaired Acquired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	103,251,000	111,117,000
Ratio of type of loan to total loans receivable	1.30%	1.40%
Credit Impaired Acquired Loans [Member] | Residential Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	340,000	342,000
Ratio of type of loan to total loans receivable	0.00%	0.00%
Credit Impaired Acquired Loans [Member] | Construction, Speculative [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	1,755,000	1,889,000
Ratio of type of loan to total loans receivable	0.00%	0.00%
Credit Impaired Acquired Loans [Member] | Land, Acquisition and Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	2,677,000	3,702,000
Ratio of type of loan to total loans receivable	0.00%	0.10%
Credit Impaired Acquired Loans [Member] | Multi Family Housing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	0	601,000
Ratio of type of loan to total loans receivable	0.00%	0.00%
Credit Impaired Acquired Loans [Member] | Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	83,657,000	87,154,000
Ratio of type of loan to total loans receivable	1.10%	1.10%
Credit Impaired Acquired Loans [Member] | Commercial and Industrial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	1,883,000	3,292,000
Ratio of type of loan to total loans receivable	0.00%	0.00%
Credit Impaired Acquired Loans [Member] | Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	12,849,000	14,040,000
Ratio of type of loan to total loans receivable	0.20%	0.20%
Credit Impaired Acquired Loans [Member] | Consumer Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, gross	$ 90,000	$ 97,000
Ratio of type of loan to total loans receivable	0.00%	0.00%