Mortgage Servicing Rights - Changes in Mortgage Servicing Rights (Detail) (Mortgage servicing rights [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Mortgage servicing rights [Member]
Servicing Asset at Amortized Cost [Line Items]
Beginning of period	$ 5,227	$ 3,276	$ 4,152	$ 2,739
Servicing rights capitalized	544	741	2,183	1,777
Amortization of servicing rights	(287)	(463)	(1,099)	(1,147)
Changes in valuation allowance		(372)	248	(187)
End of period	5,484	3,182	5,484	3,182
Mortgage loans serviced for others	$ 736,017	$ 540,735	$ 736,017	$ 540,735