Investment Securities - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2014 Security	Mar. 31, 2013	Dec. 31, 2013 Security	Dec. 31, 2012
Investment Securities [Line Items]
Held to Maturity, Amortized Cost	$ 1,813,096,000		$ 1,731,737,000
Available for sale	796,583,000		829,692,000
Fair value of trading securities	14,255,000		14,264,000
Number of security positions in the securities held to maturity portfolio in an unrealized loss position	108		133
Fair value of investments held to maturity pledged as collateral	904,300,000
Weighted-average remaining expected life of residential mortgage-backed securities held to maturity, years	9 years 2 months 12 days
Amortized Cost	821,322,000		866,904,000
Gross unrealized losses	33,265,000		46,262,000
Gross unrealized losses	33,265,000		46,262,000
Fair value of securities available for sale pledged as collateral	532,100,000
Weighted-average remaining expected life of residential mortgage-backed securities available for sale, years	5 years 9 months 18 days
Credit factors risk percentage	25.00%
(Losses) gains on securities transactions, net	(8,000)	3,958,000
Interest income on trading securities	290,000	442,000
Amortized Cost		941,000
Gross gains, Sales transactions	0	3,380,000
Other than temporary impairment losses recognized in earnings	9,792,000	33,177,000	9,990,000	33,290,000
Number of security positions in the securities available for sale portfolio in an unrealized loss position	98		99
Corporate and Other Debt Securities [Member]
Investment Securities [Line Items]
Gross unrealized losses	1,300,000
Trust Preferred Securities [Member] | Previously Other-Than-Temporarily Impaired Securities [Member]
Investment Securities [Line Items]
Available for sale	4,000,000
Amortized Cost	5,400,000
Trust Preferred Securities [Member]
Investment Securities [Line Items]
Number of security positions in the securities available for sale portfolio in an unrealized loss position	9
Trust Preferred Securities [Member] | Non-Rated [Member]
Investment Securities [Line Items]
Number of security positions in the securities held to maturity portfolio in an unrealized loss position	4
Pooled Trust Preferred Securities [Member]
Investment Securities [Line Items]
Available for sale	10,500,000
Amortized Cost	13,500,000
Gross unrealized losses	3,000,000
Number of security positions in the securities available for sale portfolio in an unrealized loss position	3		3
Pooled Trust Preferred Securities [Member] | Investment Grade [Member]
Investment Securities [Line Items]
Gross unrealized losses	1,700,000
Number of security positions in the securities available for sale portfolio in an unrealized loss position	1
Pooled Trust Preferred Securities [Member] | Non-Investment Grade [Member]
Investment Securities [Line Items]
Number of security positions in the securities available for sale portfolio in an unrealized loss position	2
Perpetual Preferred Securities [Member]
Investment Securities [Line Items]
Amortized Cost	10,000,000
Gross unrealized losses	800,000
Number of security positions in the securities available for sale portfolio in an unrealized loss position	2
Three Private Label Mortgage-Backed Securities [Member]
Investment Securities [Line Items]
Available for sale	22,900,000
Number of investment grade private label mortgage-backed securities				5
Three Private Label Mortgage-Backed Securities [Member] | Investment Grade [Member]
Investment Securities [Line Items]
Gross unrealized losses	1,300,000
Three Private Label Mortgage-Backed Securities [Member] | Previously Other-Than-Temporarily Impaired Securities [Member]
Investment Securities [Line Items]
Number of investment grade private label mortgage-backed securities				3
Three Private Label Mortgage-Backed Securities [Member] | Previously Other-Than-Temporarily Impaired Securities [Member] | Investment Grade [Member]
Investment Securities [Line Items]
Number of investment grade private label mortgage-backed securities	4
Obligations of States and Political Subdivisions [Member]
Investment Securities [Line Items]
Held to Maturity, Amortized Cost	531,931,000		545,886,000
Available for sale	37,824,000		37,700,000
Amortized Cost	39,002,000		39,112,000
Gross unrealized losses	1,277,000		2,163,000
Gross unrealized losses	1,277,000		2,163,000
Obligations of States and Political Subdivisions [Member] | Other Than Temporarily Impaired Securities [Member]
Investment Securities [Line Items]
Available for sale	18,600,000
Amortized Cost	18,400,000
Gross unrealized losses	6,700,000
Investment carrying value	569,800,000
Investment carrying value percentage	55.00%
Residential Mortgage-Backed Securities [Member]
Investment Securities [Line Items]
Held to Maturity, Amortized Cost	971,361,000		886,043,000
Available for sale	495,604,000		508,029,000
Amortized Cost	506,034,000		524,781,000
Gross unrealized losses	14,265,000		20,719,000
Gross unrealized losses	14,265,000		20,719,000
Other than temporary impairment losses recognized in earnings	$ 0