Securities (Non-Agency Collateralized Mortgage Obligations) (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Schedule of Held-to-maturity Securities [Line Items]
Book Value	$ 16,738	[1]
Original, Credit Support %	4.00%
Current, Credit Support %	9.60%
Original %, LTV, Subordination Data	54.00%
Original Credit Score, Subordination Data	717
Security 1 [Member]
Schedule of Held-to-maturity Securities [Line Items]
Original Year	2003
Book Value	1,573	[1]
S&P, Credit Rating	AA+
Moody's, Credit Rating	n/a
Original, Credit Support %	2.50%
Current, Credit Support %	6.70%
30 Day, Delinquency %, Subordination Data	2.10%
60 Day, Delinquency %, Subordination Data	0.90%
90 Day, Delinquency %, Subordination Data	1.00%
%, Foreclosure, Subordination Data	1.20%
%, OREO, Subordination Data	0.20%
%, Bankruptcy, Subordination Data	1.20%
%, Total Delinquency, Subordination Data	6.70%
Original %, LTV, Subordination Data	51.00%
Original Credit Score, Subordination Data	735
Security 2 [Member]
Schedule of Held-to-maturity Securities [Line Items]
Original Year	2003
Book Value	1,392	[1]
S&P, Credit Rating	A+
Moody's, Credit Rating	n/a
Original, Credit Support %	4.30%
Current, Credit Support %	17.10%
30 Day, Delinquency %, Subordination Data	4.50%
60 Day, Delinquency %, Subordination Data	1.80%
90 Day, Delinquency %, Subordination Data	1.60%
%, Foreclosure, Subordination Data	4.40%
%, OREO, Subordination Data	0.40%
%, Bankruptcy, Subordination Data	1.60%
%, Total Delinquency, Subordination Data	14.30%
Original %, LTV, Subordination Data	54.40%
Original Credit Score, Subordination Data	708
Security 3 [Member]
Schedule of Held-to-maturity Securities [Line Items]
Original Year	2003
Book Value	773	[1]
S&P, Credit Rating	AA-
Moody's, Credit Rating	n/a
Original, Credit Support %	2.00%
Current, Credit Support %	7.90%
30 Day, Delinquency %, Subordination Data	0.00%
60 Day, Delinquency %, Subordination Data	0.40%
90 Day, Delinquency %, Subordination Data	2.80%
%, Foreclosure, Subordination Data	2.30%
%, OREO, Subordination Data	0.30%
%, Bankruptcy, Subordination Data	0.00%
%, Total Delinquency, Subordination Data	5.80%
Original %, LTV, Subordination Data	45.90%
Original Credit Score, Subordination Data	740
Security 4 [Member]
Schedule of Held-to-maturity Securities [Line Items]
Original Year	2003
Book Value	755	[1]
S&P, Credit Rating	AA+
Moody's, Credit Rating	n/a
Original, Credit Support %	2.70%
Current, Credit Support %	20.70%
30 Day, Delinquency %, Subordination Data	0.00%
60 Day, Delinquency %, Subordination Data	0.00%
90 Day, Delinquency %, Subordination Data	0.00%
%, Foreclosure, Subordination Data	3.20%
%, OREO, Subordination Data	2.20%
%, Bankruptcy, Subordination Data	2.10%
%, Total Delinquency, Subordination Data	7.60%
Original %, LTV, Subordination Data	47.50%
Security 5 [Member]
Schedule of Held-to-maturity Securities [Line Items]
Original Year	2003
Book Value	2,656	[1]
S&P, Credit Rating	BBB+
Moody's, Credit Rating	n/a
Original, Credit Support %	2.50%
Current, Credit Support %	5.60%
30 Day, Delinquency %, Subordination Data	0.50%
60 Day, Delinquency %, Subordination Data	0.50%
90 Day, Delinquency %, Subordination Data	0.00%
%, Foreclosure, Subordination Data	2.30%
%, OREO, Subordination Data	0.00%
%, Bankruptcy, Subordination Data	1.30%
%, Total Delinquency, Subordination Data	4.60%
Original %, LTV, Subordination Data	50.10%
Original Credit Score, Subordination Data	729
Security 6 [Member]
Schedule of Held-to-maturity Securities [Line Items]
Original Year	2004
Book Value	2,498	[1]
S&P, Credit Rating	A+
Moody's, Credit Rating	Ba3
Original, Credit Support %	7.00%
Current, Credit Support %	21.40%
30 Day, Delinquency %, Subordination Data	2.30%
60 Day, Delinquency %, Subordination Data	0.20%
90 Day, Delinquency %, Subordination Data	3.30%
%, Foreclosure, Subordination Data	10.70%
%, OREO, Subordination Data	0.20%
%, Bankruptcy, Subordination Data	3.50%
%, Total Delinquency, Subordination Data	20.20%
Original %, LTV, Subordination Data	54.90%
Original Credit Score, Subordination Data	689
Security 7 [Member]
Schedule of Held-to-maturity Securities [Line Items]
Original Year	2004
Book Value	1,541	[1]
S&P, Credit Rating	AA+
Moody's, Credit Rating	n/a
Original, Credit Support %	5.30%
Current, Credit Support %	10.40%
30 Day, Delinquency %, Subordination Data	0.00%
60 Day, Delinquency %, Subordination Data	0.70%
90 Day, Delinquency %, Subordination Data	3.40%
%, Foreclosure, Subordination Data	3.90%
%, OREO, Subordination Data	0.00%
%, Bankruptcy, Subordination Data	0.80%
%, Total Delinquency, Subordination Data	8.70%
Original %, LTV, Subordination Data	44.50%
Original Credit Score, Subordination Data	732
Security 8 [Member]
Schedule of Held-to-maturity Securities [Line Items]
Original Year	2004
Book Value	789	[1]
S&P, Credit Rating	n/a
Moody's, Credit Rating	A1
Original, Credit Support %	2.50%
Current, Credit Support %	11.10%
30 Day, Delinquency %, Subordination Data	0.00%
60 Day, Delinquency %, Subordination Data	0.00%
90 Day, Delinquency %, Subordination Data	0.00%
%, Foreclosure, Subordination Data	6.10%
%, OREO, Subordination Data	0.00%
%, Bankruptcy, Subordination Data	0.00%
%, Total Delinquency, Subordination Data	6.10%
Original %, LTV, Subordination Data	53.40%
Original Credit Score, Subordination Data	728
Security 9 [Member]
Schedule of Held-to-maturity Securities [Line Items]
Original Year	2004
Book Value	1,125	[1]
S&P, Credit Rating	AA+
Moody's, Credit Rating	Baa2
Original, Credit Support %	4.40%
Current, Credit Support %	9.80%
30 Day, Delinquency %, Subordination Data	1.40%
60 Day, Delinquency %, Subordination Data	0.30%
90 Day, Delinquency %, Subordination Data	0.70%
%, Foreclosure, Subordination Data	2.80%
%, OREO, Subordination Data	0.40%
%, Bankruptcy, Subordination Data	1.60%
%, Total Delinquency, Subordination Data	7.20%
Original %, LTV, Subordination Data	53.60%
Original Credit Score, Subordination Data	733
Security 10 [Member]
Schedule of Held-to-maturity Securities [Line Items]
Original Year	2005
Book Value	$ 3,636	[1]
S&P, Credit Rating	CC
Moody's, Credit Rating	Caa1
Original, Credit Support %	5.10%
Current, Credit Support %	0.10%
30 Day, Delinquency %, Subordination Data	4.80%
60 Day, Delinquency %, Subordination Data	1.80%
90 Day, Delinquency %, Subordination Data	8.10%
%, Foreclosure, Subordination Data	8.30%
%, OREO, Subordination Data	0.90%
%, Bankruptcy, Subordination Data	2.30%
%, Total Delinquency, Subordination Data	26.30%
Original %, LTV, Subordination Data	64.60%
Original Credit Score, Subordination Data	705

[1] One acquired available for sale non-agency CMO with a December 31, 2012 book value of $23 is not included in the above table. The bond rating at acquisition was AAA and is now Baa2. This non-agency CMO is current with regards to principal and interest.