Loans and Leases (Credit Quality Indicators Credit Exposure) (Detail) (USD $)	Sep. 30, 2013		Dec. 31, 2012
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	$ 13,300,309,000		$ 12,728,082,000
Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	7,898,838,000		7,906,530,000
Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	5,477,616,000		4,988,211,000
Pass [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	6,945,646,000	[1]	6,984,897,000	[1]
Special Mention [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	425,484,000	[2]	388,627,000	[2]
Substandard [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	527,708,000	[3]	533,006,000	[3]
Performing [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	5,444,403,000		4,950,890,000
Nonperforming [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	33,213,000	[4]	37,321,000	[4]
Originated Loans And Leases [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	6,677,173,000		6,419,584,000
Originated Loans And Leases [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	4,945,290,000		4,345,874,000
Originated Loans And Leases [Member] | Pass [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	5,998,305,000	[1]	5,836,181,000	[1]
Originated Loans And Leases [Member] | Special Mention [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	334,705,000	[2]	264,402,000	[2]
Originated Loans And Leases [Member] | Substandard [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	344,163,000	[3]	319,001,000	[3]
Originated Loans And Leases [Member] | Performing [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	4,922,184,000		4,320,625,000
Originated Loans And Leases [Member] | Nonperforming [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	23,106,000	[4]	25,249,000	[4]
Purchased Loans And Leases [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	1,221,665,000		1,486,946,000
Purchased Loans And Leases [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	532,326,000		642,337,000
Purchased Loans And Leases [Member] | Pass [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	947,341,000	[1]	1,148,716,000	[1]
Purchased Loans And Leases [Member] | Special Mention [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	90,779,000	[2]	124,225,000	[2]
Purchased Loans And Leases [Member] | Substandard [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	183,545,000	[3]	214,005,000	[3]
Purchased Loans And Leases [Member] | Performing [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	522,219,000		630,265,000
Purchased Loans And Leases [Member] | Nonperforming [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	10,107,000	[4]	12,072,000	[4]
Commercial, Financial, And Agricultural [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	2,273,735,000		2,273,611,000
Commercial, Financial, And Agricultural [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	2,273,735,000		2,273,611,000
Commercial, Financial, And Agricultural [Member] | Pass [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	2,107,968,000	[1]	2,143,856,000	[1]
Commercial, Financial, And Agricultural [Member] | Special Mention [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	92,791,000	[2]	53,418,000	[2]
Commercial, Financial, And Agricultural [Member] | Substandard [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	72,976,000	[3]	76,337,000	[3]
Commercial, Financial, And Agricultural [Member] | Originated Loans And Leases [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	2,149,530,000		2,114,404,000
Commercial, Financial, And Agricultural [Member] | Originated Loans And Leases [Member] | Pass [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	2,001,420,000	[1]	2,008,548,000	[1]
Commercial, Financial, And Agricultural [Member] | Originated Loans And Leases [Member] | Special Mention [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	88,046,000	[2]	45,733,000	[2]
Commercial, Financial, And Agricultural [Member] | Originated Loans And Leases [Member] | Substandard [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	60,064,000	[3]	60,123,000	[3]
Commercial, Financial, And Agricultural [Member] | Purchased Loans And Leases [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	124,205,000		159,207,000
Commercial, Financial, And Agricultural [Member] | Purchased Loans And Leases [Member] | Pass [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	106,548,000	[1]	135,308,000	[1]
Commercial, Financial, And Agricultural [Member] | Purchased Loans And Leases [Member] | Special Mention [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	4,745,000	[2]	7,685,000	[2]
Commercial, Financial, And Agricultural [Member] | Purchased Loans And Leases [Member] | Substandard [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	12,912,000	[3]	16,214,000	[3]
Real Estate - Construction [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	765,246,000		847,781,000
Real Estate - Construction [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	647,757,000	[5]	745,220,000	[5]
Real Estate - Construction [Member] | Pass [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	510,153,000	[1],[5]	534,585,000	[1],[5]
Real Estate - Construction [Member] | Special Mention [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	61,014,000	[2],[5]	111,371,000	[2],[5]
Real Estate - Construction [Member] | Substandard [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	76,590,000	[3],[5]	99,264,000	[3],[5]
Real Estate - Construction [Member] | Originated Loans And Leases [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	557,541,000	[5]	561,250,000	[5]
Real Estate - Construction [Member] | Originated Loans And Leases [Member] | Pass [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	465,210,000	[1],[5]	439,296,000	[1],[5]
Real Estate - Construction [Member] | Originated Loans And Leases [Member] | Special Mention [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	52,792,000	[2],[5]	76,852,000	[2],[5]
Real Estate - Construction [Member] | Originated Loans And Leases [Member] | Substandard [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	39,539,000	[3],[5]	45,102,000	[3],[5]
Real Estate - Construction [Member] | Purchased Loans And Leases [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	90,216,000	[5]	183,970,000	[5]
Real Estate - Construction [Member] | Purchased Loans And Leases [Member] | Pass [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	44,943,000	[1],[5]	95,289,000	[1],[5]
Real Estate - Construction [Member] | Purchased Loans And Leases [Member] | Special Mention [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	8,222,000	[2],[5]	34,519,000	[2],[5]
Real Estate - Construction [Member] | Purchased Loans And Leases [Member] | Substandard [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	37,051,000	[3],[5]	54,162,000	[3],[5]
Real Estate Secured - Commercial [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	4,109,329,000		3,964,608,000
Real Estate Secured - Commercial [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	4,977,346,000	[6]	4,887,699,000	[6]
Real Estate Secured - Commercial [Member] | Pass [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	4,327,525,000	[1],[6]	4,306,456,000	[1],[6]
Real Estate Secured - Commercial [Member] | Special Mention [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	271,679,000	[2],[6]	223,838,000	[2],[6]
Real Estate Secured - Commercial [Member] | Substandard [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	378,142,000	[3],[6]	357,405,000	[3],[6]
Real Estate Secured - Commercial [Member] | Originated Loans And Leases [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	3,970,102,000	[6]	3,743,930,000	[6]
Real Estate Secured - Commercial [Member] | Originated Loans And Leases [Member] | Pass [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	3,531,675,000	[1],[6]	3,388,337,000	[1],[6]
Real Estate Secured - Commercial [Member] | Originated Loans And Leases [Member] | Special Mention [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	193,867,000	[2],[6]	141,817,000	[2],[6]
Real Estate Secured - Commercial [Member] | Originated Loans And Leases [Member] | Substandard [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	244,560,000	[3],[6]	213,776,000	[3],[6]
Real Estate Secured - Commercial [Member] | Purchased Loans And Leases [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	1,007,244,000	[6]	1,143,769,000	[6]
Real Estate Secured - Commercial [Member] | Purchased Loans And Leases [Member] | Pass [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	795,850,000	[1],[6]	918,119,000	[1],[6]
Real Estate Secured - Commercial [Member] | Purchased Loans And Leases [Member] | Special Mention [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	77,812,000	[2],[6]	82,021,000	[2],[6]
Real Estate Secured - Commercial [Member] | Purchased Loans And Leases [Member] | Substandard [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	133,582,000	[3],[6]	143,629,000	[3],[6]
Real Estate Secured - Residential [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	4,145,522,000		4,065,818,000
Real Estate Secured - Residential [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	3,394,994,000		3,245,288,000
Real Estate Secured - Residential [Member] | Performing [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	3,364,052,000		3,210,145,000
Real Estate Secured - Residential [Member] | Nonperforming [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	30,942,000	[4]	35,143,000	[4]
Real Estate Secured - Residential [Member] | Originated Loans And Leases [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	2,869,956,000		2,614,431,000
Real Estate Secured - Residential [Member] | Originated Loans And Leases [Member] | Performing [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	2,849,108,000		2,591,349,000
Real Estate Secured - Residential [Member] | Originated Loans And Leases [Member] | Nonperforming [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	20,848,000	[4]	23,082,000	[4]
Real Estate Secured - Residential [Member] | Purchased Loans And Leases [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	525,038,000		630,857,000
Real Estate Secured - Residential [Member] | Purchased Loans And Leases [Member] | Performing [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	514,944,000		618,796,000
Real Estate Secured - Residential [Member] | Purchased Loans And Leases [Member] | Nonperforming [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	10,094,000	[4]	12,061,000	[4]
Consumer [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	935,117,000		842,552,000
Consumer [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	935,117,000		842,552,000
Consumer [Member] | Performing [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	934,481,000		841,964,000
Consumer [Member] | Nonperforming [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	636,000	[4]	588,000	[4]
Consumer [Member] | Originated Loans And Leases [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	927,829,000		831,072,000
Consumer [Member] | Originated Loans And Leases [Member] | Performing [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	927,206,000		830,495,000
Consumer [Member] | Originated Loans And Leases [Member] | Nonperforming [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	623,000	[4]	577,000	[4]
Consumer [Member] | Purchased Loans And Leases [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	7,288,000		11,480,000
Consumer [Member] | Purchased Loans And Leases [Member] | Performing [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	7,275,000		11,469,000
Consumer [Member] | Purchased Loans And Leases [Member] | Nonperforming [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	13,000	[4]	11,000	[4]
Leases [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	1,147,505,000		900,371,000
Leases [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	1,147,505,000		900,371,000
Leases [Member] | Performing [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	1,145,870,000		898,781,000
Leases [Member] | Nonperforming [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	1,635,000	[4]	1,590,000	[4]
Leases [Member] | Originated Loans And Leases [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	1,147,505,000		900,371,000
Leases [Member] | Originated Loans And Leases [Member] | Performing [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	1,145,870,000		898,781,000
Leases [Member] | Originated Loans And Leases [Member] | Nonperforming [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	1,635,000	[4]	1,590,000	[4]
Leases [Member] | Purchased Loans And Leases [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	0		0
Leases [Member] | Purchased Loans And Leases [Member] | Performing [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	0		0
Leases [Member] | Purchased Loans And Leases [Member] | Nonperforming [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	$ 0	[4]	$ 0	[4]

[1] Includes loans identified as having acceptable risk, which are loans for which the possibility of loss is considered unlikely.

[2] Includes loans considered potentially weak; however, no loss of principal or interest is anticipated.

[3] Includes loans that are inadequately protected by the current net-worth and paying capacity of the borrower or by the collateral pledged, if any. Loss of principal or interest is considered reasonably possible or likely.

[4] Includes loans that are on non-accrual status or past due ninety days or more.

[5] Includes only construction loans granted to commercial customers. Construction loans for individuals are included in Real Estate – Secured – Residential, below.

[6] Includes loans obtained for commercial purposes that are also secured by residential real estate.