Loans and Leases (Credit Quality Indicators Credit Exposure) (Detail) (USD $)	Jun. 30, 2014		Dec. 31, 2013
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	$ 13,600,254,000		$ 13,503,392,000
Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	7,939,975,000		7,969,557,000
Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	5,727,178,000		5,606,529,000
Pass [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	7,179,923,000	[1]	7,155,065,000	[1]
Special Mention [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	337,052,000	[2]	363,772,000	[2]
Substandard [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	423,000,000	[3]	450,720,000	[3]
Performing [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	5,699,541,000		5,576,068,000
Nonperforming [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	27,637,000	[4]	30,461,000	[4]
Originated Loans And Leases [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	6,899,667,000		6,833,939,000
Originated Loans And Leases [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	5,259,607,000		5,097,007,000
Originated Loans And Leases [Member] | Pass [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	6,355,330,000	[1]	6,270,856,000	[1]
Originated Loans And Leases [Member] | Special Mention [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	247,795,000	[2]	277,533,000	[2]
Originated Loans And Leases [Member] | Substandard [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	296,542,000	[3]	285,550,000	[3]
Originated Loans And Leases [Member] | Performing [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	5,240,972,000		5,077,555,000
Originated Loans And Leases [Member] | Nonperforming [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	18,635,000	[4]	19,452,000	[4]
Purchased Loans And Leases [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	1,040,308,000		1,135,618,000
Purchased Loans And Leases [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	467,571,000		509,522,000
Purchased Loans And Leases [Member] | Pass [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	824,593,000	[1]	884,209,000	[1]
Purchased Loans And Leases [Member] | Special Mention [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	89,257,000	[2]	86,239,000	[2]
Purchased Loans And Leases [Member] | Substandard [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	126,458,000	[3]	165,170,000	[3]
Purchased Loans And Leases [Member] | Performing [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	458,569,000		498,513,000
Purchased Loans And Leases [Member] | Nonperforming [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	9,002,000	[4]	11,009,000	[4]
Commercial, Financial, And Agricultural [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	2,422,931,000		2,394,847,000
Commercial, Financial, And Agricultural [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	2,422,931,000		2,394,847,000
Commercial, Financial, And Agricultural [Member] | Pass [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	2,275,855,000	[1]	2,242,782,000	[1]
Commercial, Financial, And Agricultural [Member] | Special Mention [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	68,315,000	[2]	79,382,000	[2]
Commercial, Financial, And Agricultural [Member] | Substandard [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	78,761,000	[3]	72,683,000	[3]
Commercial, Financial, And Agricultural [Member] | Originated Loans And Leases [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	2,302,955,000		2,269,214,000
Commercial, Financial, And Agricultural [Member] | Originated Loans And Leases [Member] | Pass [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	2,168,434,000	[1]	2,133,884,000	[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	62,990,000	[2]	75,162,000	[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	71,531,000	[3]	60,168,000	[3]
Commercial, Financial, And Agricultural [Member] | Purchased Loans And Leases [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	119,976,000		125,633,000
Commercial, Financial, And Agricultural [Member] | Purchased Loans And Leases [Member] | Pass [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	107,421,000	[1]	108,898,000	[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	5,325,000	[2]	4,220,000	[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	7,230,000	[3]	12,515,000	[3]
Real Estate - Construction [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	748,181,000		735,877,000
Real Estate - Construction [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	627,626,000	[5]	609,715,000	[5]
Real Estate - Construction [Member] | Pass [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	541,892,000	[1],[5]	503,167,000	[1],[5]
Real Estate - Construction [Member] | Special Mention [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	39,686,000	[2],[5]	53,718,000	[2],[5]
Real Estate - Construction [Member] | Substandard [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	46,048,000	[3],[5]	52,830,000	[3],[5]
Real Estate - Construction [Member] | Originated Loans And Leases [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	569,847,000	[5]	542,587,000	[5]
Real Estate - Construction [Member] | Originated Loans And Leases [Member] | Pass [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	517,720,000	[1],[5]	478,097,000	[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	20,374,000	[2],[5]	33,907,000	[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	31,753,000	[3],[5]	30,583,000	[3],[5]
Real Estate - Construction [Member] | Purchased Loans And Leases [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	57,779,000	[5]	67,128,000	[5]
Real Estate - Construction [Member] | Purchased Loans And Leases [Member] | Pass [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	24,172,000	[1],[5]	25,070,000	[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	19,312,000	[2],[5]	19,811,000	[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	14,295,000	[3],[5]	22,247,000	[3],[5]
Real Estate Secured - Commercial [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	4,053,990,000		4,068,816,000
Real Estate Secured - Commercial [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	4,889,418,000	[6]	4,964,995,000	[6]
Real Estate Secured - Commercial [Member] | Pass [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	4,362,176,000	[1],[6]	4,409,116,000	[1],[6]
Real Estate Secured - Commercial [Member] | Special Mention [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	229,051,000	[2],[6]	230,672,000	[2],[6]
Real Estate Secured - Commercial [Member] | Substandard [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	298,191,000	[3],[6]	325,207,000	[3],[6]
Real Estate Secured - Commercial [Member] | Originated Loans And Leases [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	4,026,865,000	[6]	4,022,138,000	[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	3,669,176,000	[1],[6]	3,658,875,000	[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	164,431,000	[2],[6]	168,464,000	[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	193,258,000	[3],[6]	194,799,000	[3],[6]
Real Estate Secured - Commercial [Member] | Purchased Loans And Leases [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	862,553,000	[6]	942,857,000	[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	693,000,000	[1],[6]	750,241,000	[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	64,620,000	[2],[6]	62,208,000	[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	104,933,000	[3],[6]	130,408,000	[3],[6]
Real Estate Secured - Residential [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	4,178,842,000		4,204,430,000
Real Estate Secured - Residential [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	3,463,969,000		3,434,413,000
Real Estate Secured - Residential [Member] | Performing [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	3,437,854,000		3,406,469,000
Real Estate Secured - Residential [Member] | Nonperforming [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	26,115,000	[4]	27,944,000	[4]
Real Estate Secured - Residential [Member] | Originated Loans And Leases [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	3,002,617,000		2,931,484,000
Real Estate Secured - Residential [Member] | Originated Loans And Leases [Member] | Performing [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	2,985,504,000		2,914,547,000
Real Estate Secured - Residential [Member] | Originated Loans And Leases [Member] | Nonperforming [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	17,113,000	[4]	16,937,000	[4]
Real Estate Secured - Residential [Member] | Purchased Loans And Leases [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	461,352,000		502,929,000
Real Estate Secured - Residential [Member] | Purchased Loans And Leases [Member] | Performing [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	452,350,000		491,922,000
Real Estate Secured - Residential [Member] | Purchased Loans And Leases [Member] | Nonperforming [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	9,002,000	[4]	11,007,000	[4]
Consumer [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	962,618,000		953,000,000
Consumer [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	962,618,000		953,000,000
Consumer [Member] | Performing [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	962,284,000		951,970,000
Consumer [Member] | Nonperforming [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	334,000	[4]	1,030,000	[4]
Consumer [Member] | Originated Loans And Leases [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	956,399,000		946,407,000
Consumer [Member] | Originated Loans And Leases [Member] | Performing [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	956,065,000		945,379,000
Consumer [Member] | Originated Loans And Leases [Member] | Nonperforming [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	334,000	[4]	1,028,000	[4]
Consumer [Member] | Purchased Loans And Leases [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	6,219,000		6,593,000
Consumer [Member] | Purchased Loans And Leases [Member] | Performing [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	6,219,000		6,591,000
Consumer [Member] | Purchased Loans And Leases [Member] | Nonperforming [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	0	[4]	2,000	[4]
Leases [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	1,300,591,000		1,219,116,000
Leases [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	1,300,591,000		1,219,116,000
Leases [Member] | Performing [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	1,299,403,000		1,217,629,000
Leases [Member] | Nonperforming [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	1,188,000	[4]	1,487,000	[4]
Leases [Member] | Originated Loans And Leases [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	1,300,591,000		1,219,116,000
Leases [Member] | Originated Loans And Leases [Member] | Performing [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	1,299,403,000		1,217,629,000
Leases [Member] | Originated Loans And Leases [Member] | Nonperforming [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	1,188,000	[4]	1,487,000	[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.