Investment Securities - Additional Information (Detail) (USD $)	1 Months Ended	12 Months Ended									12 Months Ended			12 Months Ended					12 Months Ended						12 Months Ended
	Oct. 31, 2013	Dec. 31, 2013 Security Y	Dec. 31, 2012 Security	Dec. 31, 2011	Dec. 31, 2013 Corporate and other debt securities [Member]	Dec. 31, 2013 Single-Issuer Bank Trust Preferred Securities [Member]	Dec. 31, 2012 Single-Issuer Bank Trust Preferred Securities [Member]	Dec. 31, 2013 Trust preferred securities [Member]	Sep. 30, 2012 Trust preferred securities [Member]	Dec. 31, 2011 Trust preferred securities [Member]	Dec. 31, 2011 Residential mortgage-backed securities [Member]	Dec. 31, 2013 Trust Preferred Securities [Member] Securities	Dec. 31, 2013 Trust Preferred Securities [Member] Non-Rated [Member]	Dec. 31, 2013 Three Private Label Mortgage-Backed Securities [Member]	Dec. 31, 2013 Three Private Label Mortgage-Backed Securities [Member] Investment Grade [Member] Securities	Dec. 31, 2013 Three Private Label Mortgage-Backed Securities [Member] Previously Other-Than-Temporarily Impaired Securities [Member] Investment Grade [Member] Securities	Dec. 31, 2013 Several Investment Grade Residential Mortgage-Backed Securities [Member] Investment Grade [Member]	Dec. 31, 2013 Perpetual Preferred Securities [Member] Security	Dec. 31, 2013 Pooled Trust Preferred Securities [Member] Securities	Dec. 31, 2012 Pooled Trust Preferred Securities [Member] Securities	Dec. 31, 2013 Pooled Trust Preferred Securities [Member] Investment Grade [Member] Securities	Dec. 31, 2013 Pooled Trust Preferred Securities [Member] Non-Investment Grade [Member] Securities	Dec. 31, 2013 Obligations of states and political subdivisions [Member]	Dec. 31, 2012 Obligations of states and political subdivisions [Member]	Dec. 31, 2013 Obligations of states and political subdivisions [Member] Other Than Temporarily Impaired Securities [Member]
Investment Securities [Line Items]
Held to maturity, fair value		$ 1,711,427,000	$ 1,657,950,000																				$ 543,151,000	$ 531,966,000
Available for sale		829,692,000	807,816,000																10,300,000				37,700,000	16,627,000	17,800,000
Fair value of trading securities		14,264,000	22,157,000			14,300,000	22,200,000
Number of security positions in the securities available for sale portfolio in an unrealized loss position		99	74									10						2	3	3	1	2
Number of security positions in the securities held to maturity portfolio in an unrealized loss position		133	34										4
Fair value of investments held to maturity pledged as collateral		833,600,000
Weighted-average remaining expected life of residential mortgage-backed securities held to maturity, years		7.5
Gross unrealized losses		46,262,000	19,479,000		2,100,000										7,700,000	1,200,000	11,800,000	800,000	3,300,000				2,163,000
Number of investment grade private label mortgage-backed securities															5	1
Amortized cost		866,904,000	813,474,000															10,000,000	13,600,000				39,112,000	16,210,000	18,400,000
Gross unrealized losses		46,262,000	19,479,000																		1,700,000		2,163,000		12,900,000
Fair value of securities available for sale pledged as collateral		498,800,000
Weighted-average remaining expected life of residential mortgage-backed securities available for sale, years		5.3
Investments held		0
Investment carrying value																									583,600,000
Investment carrying value percentage																									57.00%
Credit factors risk percentage		25.00%
Other-than-temporarily impaired trust preferred securities, amortized cost	41,800,000																		5,400,000
Sale of net proceeds of debt securities	52,500,000
Realized gain on securities	10,700,000
Impairment charge part of combined amortized cost of the securities								0	4,500,000	18,300,000
Other-than-temporary impairment charges attributable to credit on trust preferred securities			4,500,000	18,300,000
Other-than-temporarily impaired trust preferred securities, fair value																			3,800,000
Recognized impairment charges			722,000
Other-than-temporarily impaired mortgage-backed securities, amortized cost														24,600,000
Other-than-temporarily impaired mortgage-backed securities, fair value														24,800,000
Gross gains on sales transactions		14,098,000	6,621,000	31,456,000															10,700,000
Gross losses on the early redemption			5,300,000
Gross gains on sales transactions				651,700,000							31,500,000
Interest income on trading securities		$ 1,400,000	$ 1,800,000	$ 2,100,000