Acquisitions - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended				3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 WNB Bancshares, Inc. [Member]	May 30, 2014 WNB Bancshares, Inc. [Member]	Jun. 30, 2014 Acquisition-related Costs [Member]	Jun. 30, 2014 Acquisition-related Costs [Member]	Dec. 31, 2013 Acquisition-related Costs [Member]
Business Acquisition [Line Items]
Preliminary purchase price allocation						$ 198,121,000
Business Acquisition, Equity Interest Issued or Issuable, Value Assigned						149,000,000
Common stock number of shares issued for consideration					2,000,000
Amount of cash consideration					49,100,000
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life					10 years
Noninterest Expense	163,970,000	149,758,000	321,911,000	305,572,000			4,800,000	6,000,000	1,400,000
Other	$ 45,800,000	$ 37,373,000	$ 84,424,000	$ 78,858,000