Mortgage Banking Activities - Valuation Allowance for Mortgage Servicing Rights (Detail) (USD $)	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Mortgage Banking [Abstract]
Balance, beginning of year	$ (680,000)	$ (1,785,000)
Impairment charges		(1,179,000)
Recoveries	676,000	948,000
Balance, end of year	$ (4,000)	$ (2,016,000)