Derivative Instruments and Hedging Activities - Income for derivatives not designated as hedging instruments (Detail) (Not designated as hedging instrument [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Income for derivatives not designated as hedging instruments	$ (555)	$ 242	$ (785)	$ 837
Net gain (loss) on mortgage banking activities [Member] | Interest rate locks with customers [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Income for derivatives not designated as hedging instruments	(1,549)	725	(1,611)	947
Net gain (loss) on mortgage banking activities [Member] | Forward loan sale commitments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Income for derivatives not designated as hedging instruments	$ 994	$ (483)	$ 826	$ (110)