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		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Income for derivatives not designated as hedging instruments	$ (220)	$ 777	$ (1,005)	$ 1,614
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	913	1,394	(698)	2,341
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	$ (1,133)	$ (617)	$ (307)	$ (727)