Retail Repurchase Agreements And Other Short Term Borrowings (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Short-term Debt [Line Items]
Retail repurchase agreements carrying amount	$ 51,929	$ 63,613	$ 86,243
Retail repurchase agreements average	63,864	73,543	86,726
Retail repurchase agreements maximum	$ 73,130	$ 79,529	$ 97,884
Retail Repurchase Agreements Interest Rate	0.20%	0.20%	0.30%
Retail Repurchase Agreements Average Interest Rate	0.28%	0.26%	0.30%