Mortgage Servicing Rights (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2012	Dec. 31, 2011
Mortgage Servicing Rights [Line Items]
Fair value of mortgage servicing rights portfolio	$ 6,260	$ 7,120
Discount rate	9.00%	9.00%
Weighted average default rate	1.50%	1.50%
Minimum
Mortgage Servicing Rights [Line Items]
Prepayment speed range	220.00%	221.00%
Maximum
Mortgage Servicing Rights [Line Items]
Prepayment speed range	550.00%	550.00%