Business Combinations (All Other Acquisitions) (Detail) (USD $)	3 Months Ended	14 Months Ended	24 Months Ended	0 Months Ended
	Mar. 31, 2013	Mar. 31, 2013 financial_institution	Dec. 31, 2011 financial_institution	Dec. 12, 2012 HPK Financial Corporation [Member] locations	Apr. 13, 2012 Suburban Bank & Trust Company [Member]	Mar. 30, 2012 Suburban Bank & Trust Company [Member]	Jun. 08, 2012 Macquarie Premium Funding Inc [Member]
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition				Dec. 12, 2012	Apr. 13, 2012	Mar. 30, 2012	Jun. 08, 2012
Number of locations				2
Number of FDIC assisted banks acquired		3	6
Business acquisition, loans acquired				$ 118,500,000	$ 3,000,000		$ 213,000,000
Fair value of assets acquired, at the acquisition date				371,600,000
Liabilities Assumed				344,100,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deposits				243,800,000	52,000,000
Additional goodwill recorded on acquisition	0			12,600,000	1,500,000	1,800,000	21,900,000
Assets under Management, Carrying Amount						$ 160,000,000