Borrowed Funds - Additional Information (Detail) (USD $)	12 Months Ended										0 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Subordinated notes [Member]	Dec. 31, 2013 FHLB [Member]	Dec. 31, 2012 FHLB [Member]	Dec. 31, 2013 Long-term borrowings [Member]	Dec. 31, 2012 Long-term borrowings [Member]	Dec. 31, 2013 Securities Sold under Agreements to Repurchase [Member]	Dec. 31, 2012 Securities Sold under Agreements to Repurchase [Member]	Sep. 27, 2013 Subordinated debentures [Member]
Debt Instrument [Line Items]
Weighted average interest rate for short-term borrowings	0.28%	0.26%
Weighted average interest rate for long-term borrowings					3.89%	3.86%			4.07%	4.07%
Collateralized letter of credit					$ 400,000,000
Interest expense recorded on FHLB advances	78,400,000	79,500,000	86,600,000
Callable FHLB advances with scheduled maturities beyond 2017	455,000,000
Callable FHLB advances interest rates range, low	2.27%
Callable FHLB advances interest rates range, high	4.04%
Securities sold under agreements to repurchase							587,500,000	587,500,000
Interest expense on securities sold under repurchase agreements	24,300,000	24,600,000	25,000,000
Subordinated notes				100,000,000			221,757,000	100,000,000			125,000,000
Subordinated notes, interest rate				5.00%							5.125%
Subordinated notes, due date				Jul. 15, 2015							Sep. 27, 2023
Net carrying value of subordinated debentures	121,800,000
Interest expense on subordinated debentures	1,700,000
Fair value of securities	$ 1,300,000,000	$ 1,200,000,000