Business Combinations (FDIC Assisted Transactions) (Detail) (USD $)	3 Months Ended		9 Months Ended						0 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Jun. 30, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2011	Feb. 10, 2012 Charter National [Member]	Jul. 20, 2012 Second Federal [Member]		Sep. 28, 2012 First United Bank [Member]
Business Acquisition [Line Items]
Date of acquisition									Feb. 10, 2012	Jul. 20, 2012		Sep. 28, 2012
Fair value of assets acquired, at the acquisition date									$ 92,355,000	$ 171,625,000		$ 328,408,000
Fair value of loans acquired, at the acquisition date									45,555,000	0		77,964,000
Fair value of liabilities assumed, at the acquisition date									91,570,000	171,582,000		321,734,000
Fair value of reimbursable losses, at the acquisition date	100,313,000	238,305,000	100,313,000	238,305,000	137,681,000	208,160,000	222,568,000	344,251,000	13,164,000	0	[1]	67,190,000
Gain on bargain purchase recognized	0	6,633,000	0	7,418,000					785,000	43,000		6,675,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets Subject to Loss Sharing										$ 0

[1] As no assets subject to loss sharing agreements were acquired in the acquisition of Second Federal, there was no fair value of reimbursable losses.