Assets measured at fair value on nonrecurring basis (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012		Sep. 30, 2011
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale	$ 0
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale	9,387
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale	342,287
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans	11,887	[1]	109,694	[1]
Loans held-for-sale	102,092	[2]	84,368	[2]
Other real estate owned	93,560	[3]	23,735	[4]
Other Repossessed Assets	120	[3]	109	[4]
Assets Held-for-sale, Long Lived	0	[5]
Total	207,659		217,906
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans	0	[1]	0	[1]
Loans held-for-sale	0	[2]	0	[2]
Other real estate owned	0	[3]	0	[4]
Other Repossessed Assets	0	[3]	0	[4]
Assets Held-for-sale, Long Lived	0	[5]
Total	0		0
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans	0	[1]	0	[1]
Loans held-for-sale	0	[2]	0	[2]
Other real estate owned	0	[3]	0	[4]
Other Repossessed Assets	0	[3]	0	[4]
Assets Held-for-sale, Long Lived	0	[5]
Total	0		0
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans	11,887	[1]	109,694	[1]
Loans held-for-sale	102,092	[2]	84,368	[2]
Other real estate owned	93,560	[3]	23,735	[4]
Other Repossessed Assets	120	[3]	109	[4]
Assets Held-for-sale, Long Lived	0	[5]
Total	207,659		217,906
Fair Value, Measurements, Nonrecurring [Member] | Unrealized Gain (Loss or Write-down) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans	(12,206)	[1]	(17,181)	[1]
Loans held-for-sale	(41,706)	[2]	(29,197)	[2]
Other real estate owned	(25,795)	[3]	(12,008)	[4]
Other Repossessed Assets	(303)	[3]	(590)	[4]
Assets Held-for-sale, Long Lived	(123)	[5]
Total	$ (80,133)		$ (58,976)

[1] Relates mostly to certain impaired collateral dependent loans. The impairment was measured based on the fair value of the collateral, which is derived from appraisals that take into consideration prices in observed transactions involving similar assets in similar locations, in accordance with the provisions of ASC Section 310-10-35.

[2] Relates to lower of cost or fair value adjustments on loans held-for-sale and loans transferred from loans held-in-portfolio to loans held-for-sale.

[3] Represents the fair value of foreclosed real estate and other collateral owned that were written down to their fair value. Costs to sell excluded from the reported fair value amount were $6 million at September 30, 2012.

[4] Represents the fair value of foreclosed real estate and other collateral owned that were written down to their fair value. Costs to sell excluded from the reported fair value amount were $2 million at September 30, 2011.

[5] Represents the fair value of long-lived assets held-for-sale that were written down to their fair value.