Short-term Borrowings - Summary of Short-Term Borrowings (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Short-term Debt [Line Items]
Short-term Debt	$ 626,615	$ 356,227	$ 312,777
Average Balance	478,388	402,196	182,864
Average Rate	0.26%	0.27%	0.40%
Federal funds purchased [Member]
Short-term Debt [Line Items]
Short-term Debt	16,000	34,000	75,300
Average Balance	11,982	47,727	15,642
Average Rate	0.36%	0.27%	0.26%
Borrowings from FHLB [Member]
Short-term Debt [Line Items]
Short-term Debt	478,100	178,100	84,000
Average Balance	335,449	214,703	7,537
Average Rate	0.27%	0.25%	0.21%
Securities sold under agreements to repurchase [Member]
Short-term Debt [Line Items]
Short-term Debt	132,515	144,127	153,477
Average Balance	130,957	139,766	155,551
Average Rate	0.25%	0.28%	0.43%
Treasury, tax and loan note option [Member]
Short-term Debt [Line Items]
Short-term Debt	0	0	0
Average Balance	0	0	4,134
Average Rate	0.00%	0.00%	0.00%
Maximum [Member]
Short-term Debt [Line Items]
Short-term Debt	$ 626,615	$ 486,144	$ 312,777
Weighted Average [Member]
Short-term Debt [Line Items]
Average Rate	0.27%	0.25%	0.28%