Fair Value of Financial Instruments (Detail) - Quantitative information regarding the assumptions used for valuing Level 3 assets (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2012 Discounted Cash Flow [Member] Discount margin to LIBOR [Member] Minimum [Member] Collateralized Debt Obligations [Member]	Dec. 31, 2012 Discounted Cash Flow [Member] Discount margin to LIBOR [Member] Maximum [Member] Collateralized Debt Obligations [Member]	Dec. 31, 2012 Discounted Cash Flow [Member] Discount margin to LIBOR [Member] Weighted Average [Member] Collateralized Debt Obligations [Member]	Dec. 31, 2012 Discounted Cash Flow [Member] Discount margin to LIBOR [Member] Collateralized Debt Obligations [Member]		Dec. 31, 2012 Discounted Cash Flow [Member] Constant default rate [Member] Minimum [Member] Collateralized Debt Obligations [Member]	Dec. 31, 2012 Discounted Cash Flow [Member] Constant default rate [Member] Maximum [Member] Collateralized Debt Obligations [Member]	Dec. 31, 2012 Discounted Cash Flow [Member] Constant default rate [Member] Weighted Average [Member] Collateralized Debt Obligations [Member]	Dec. 31, 2012 Discounted Cash Flow [Member] Constant default rate [Member] Collateralized Debt Obligations [Member]		Dec. 31, 2012 Discounted Cash Flow [Member] Constant prepayment rate [Member] Weighted Average [Member] Mortgage Servicing Rights [Member]	Dec. 31, 2012 Discounted Cash Flow [Member] Constant prepayment rate [Member] Mortgage Servicing Rights [Member]		Dec. 31, 2012 Discounted Cash Flow [Member] Discount Rate [Member] Weighted Average [Member] Mortgage Servicing Rights [Member]	Dec. 31, 2012 Discounted Cash Flow [Member] Discount Rate [Member] Mortgage Servicing Rights [Member]		Dec. 31, 2012 Default percentage [Member] Minimum [Member]	Dec. 31, 2012 Default percentage [Member] Maximum [Member]	Dec. 31, 2012 Default percentage [Member] Weighted Average [Member]	Dec. 31, 2012 Delinquency percentage [Member] Weighted Average [Member]	Sep. 30, 2010 Minimum [Member]	Sep. 30, 2010 Maximum [Member]
Fair Value (in Dollars)					$ 3,332	[1]				$ 3,332	[1]		$ 13,910	[1]		$ 13,910	[1]
Valuation Technique					Discounted cash flow	[1]				Discounted cash flow	[1]		Discounted cash flow	[1]		Discounted cash flow	[1]
Range (Weighted Average)	2.50%	10.50%	16.80%	(12.38%)			0.25%	0.88%	(0.41%)			16.80%			10.44%			14.67%	51.61%	(33.67%)	1.77%	2.20%	2.70%

[1] Other level 3 securities totaling $1.6 million are valued based on data provided by the issuer