Loans and Leases (Credit Quality Indicators Credit Exposure) (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013		Dec. 31, 2012
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	$ 13,157,762		$ 12,894,741
Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	7,853,553		7,906,530
Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	5,304,209		4,988,211
Pass [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	6,910,068	[1]	6,984,897	[1]
Special Mention [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	446,108	[2]	388,627	[2]
Substandard [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	497,377	[3]	533,006	[3]
Performing Financing Receivable [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	5,267,504		4,950,890
Nonperforming Financing Receivable [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	36,705	[4]	37,321	[4]
Originated Loans And Leases [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	6,567,866		6,419,584
Originated Loans And Leases [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	4,732,955		4,345,874
Originated Loans And Leases [Member] | Pass [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	5,919,507	[1]	5,836,181	[1]
Originated Loans And Leases [Member] | Special Mention [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	346,904	[2]	264,402	[2]
Originated Loans And Leases [Member] | Substandard [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	301,455	[3]	319,001	[3]
Originated Loans And Leases [Member] | Performing Financing Receivable [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	4,707,256		4,320,625
Originated Loans And Leases [Member] | Nonperforming Financing Receivable [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	25,699	[4]	25,249	[4]
Purchased Loans And Leases [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	1,285,687		1,486,946
Purchased Loans And Leases [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	571,254		642,337
Purchased Loans And Leases [Member] | Pass [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	990,561	[1]	1,148,716	[1]
Purchased Loans And Leases [Member] | Special Mention [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	99,204	[2]	124,225	[2]
Purchased Loans And Leases [Member] | Substandard [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	195,922	[3]	214,005	[3]
Purchased Loans And Leases [Member] | Performing Financing Receivable [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	560,248		630,265
Purchased Loans And Leases [Member] | Nonperforming Financing Receivable [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	11,006	[4]	12,072	[4]
Commercial, Financial, And Agricultural [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	2,289,159		2,273,611
Commercial, Financial, And Agricultural [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	2,289,159		2,273,611
Commercial, Financial, And Agricultural [Member] | Pass [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	2,133,785	[1]	2,143,856	[1]
Commercial, Financial, And Agricultural [Member] | Special Mention [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	93,681	[2]	53,418	[2]
Commercial, Financial, And Agricultural [Member] | Substandard [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	61,693	[3]	76,337	[3]
Commercial, Financial, And Agricultural [Member] | Originated Loans And Leases [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	2,153,251		2,114,404
Commercial, Financial, And Agricultural [Member] | Originated Loans And Leases [Member] | Pass [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	2,017,786	[1]	2,008,548	[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	87,745	[2]	45,733	[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	47,720	[3]	60,123	[3]
Commercial, Financial, And Agricultural [Member] | Purchased Loans And Leases [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	135,908		159,207
Commercial, Financial, And Agricultural [Member] | Purchased Loans And Leases [Member] | Pass [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	115,999	[1]	135,308	[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	5,936	[2]	7,685	[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	13,973	[3]	16,214	[3]
Real Estate - Construction [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	769,722		847,781
Real Estate - Construction [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	656,464	[5]	745,220	[5]
Real Estate - Construction [Member] | Pass [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	494,750	[1],[5]	534,585	[1],[5]
Real Estate - Construction [Member] | Special Mention [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	81,399	[2],[5]	111,371	[2],[5]
Real Estate - Construction [Member] | Substandard [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	80,315	[3],[5]	99,264	[3],[5]
Real Estate - Construction [Member] | Originated Loans And Leases [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	548,436	[5]	561,250	[5]
Real Estate - Construction [Member] | Originated Loans And Leases [Member] | Pass [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	438,951	[1],[5]	439,296	[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	67,495	[2],[5]	76,852	[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	41,990	[3],[5]	45,102	[3],[5]
Real Estate - Construction [Member] | Purchased Loans And Leases [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	108,028	[5]	183,970	[5]
Real Estate - Construction [Member] | Purchased Loans And Leases [Member] | Pass [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	55,799	[1],[5]	95,289	[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	13,904	[2],[5]	34,519	[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	38,325	[3],[5]	54,162	[3],[5]
Real Estate Secured - Commercial [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	4,029,454		3,964,608
Real Estate Secured - Commercial [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	4,907,930	[6]	4,887,699	[6]
Real Estate Secured - Commercial [Member] | Pass [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	4,281,533	[1],[6]	4,306,456	[1],[6]
Real Estate Secured - Commercial [Member] | Special Mention [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	271,028	[2],[6]	223,838	[2],[6]
Real Estate Secured - Commercial [Member] | Substandard [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	355,369	[3],[6]	357,405	[3],[6]
Real Estate Secured - Commercial [Member] | Originated Loans And Leases [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	3,866,179	[6]	3,743,930	[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	3,462,770	[1],[6]	3,388,337	[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	191,664	[2],[6]	141,817	[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	211,745	[3],[6]	213,776	[3],[6]
Real Estate Secured - Commercial [Member] | Purchased Loans And Leases [Member] | Commercial Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	1,041,751	[6]	1,143,769	[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	818,763	[1],[6]	918,119	[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	79,364	[2],[6]	82,021	[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	143,624	[3],[6]	143,629	[3],[6]
Real Estate Secured - Residential [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	4,098,938		4,065,818
Real Estate Secured - Residential [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	3,333,720		3,245,288
Real Estate Secured - Residential [Member] | Performing Financing Receivable [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	3,298,848		3,210,145
Real Estate Secured - Residential [Member] | Nonperforming Financing Receivable [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	34,872	[4]	35,143	[4]
Real Estate Secured - Residential [Member] | Originated Loans And Leases [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	2,770,933		2,614,431
Real Estate Secured - Residential [Member] | Originated Loans And Leases [Member] | Performing Financing Receivable [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	2,747,045		2,591,349
Real Estate Secured - Residential [Member] | Originated Loans And Leases [Member] | Nonperforming Financing Receivable [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	23,888	[4]	23,082	[4]
Real Estate Secured - Residential [Member] | Purchased Loans And Leases [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	562,787		630,857
Real Estate Secured - Residential [Member] | Purchased Loans And Leases [Member] | Performing Financing Receivable [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	551,803		618,796
Real Estate Secured - Residential [Member] | Purchased Loans And Leases [Member] | Nonperforming Financing Receivable [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	10,984	[4]	12,061	[4]
Consumer [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	908,328		842,552
Consumer [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	908,328		842,552
Consumer [Member] | Performing Financing Receivable [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	907,703		841,964
Consumer [Member] | Nonperforming Financing Receivable [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	625	[4]	588	[4]
Consumer [Member] | Originated Loans And Leases [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	899,861		831,072
Consumer [Member] | Originated Loans And Leases [Member] | Performing Financing Receivable [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	899,258		830,495
Consumer [Member] | Originated Loans And Leases [Member] | Nonperforming Financing Receivable [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	603	[4]	577	[4]
Consumer [Member] | Purchased Loans And Leases [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	8,467		11,480
Consumer [Member] | Purchased Loans And Leases [Member] | Performing Financing Receivable [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	8,445		11,469
Consumer [Member] | Purchased Loans And Leases [Member] | Nonperforming Financing Receivable [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	22	[4]	11	[4]
Leases [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	1,062,161		900,371
Leases [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	1,062,161		900,371
Leases [Member] | Performing Financing Receivable [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	1,060,953		898,781
Leases [Member] | Nonperforming Financing Receivable [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	1,208	[4]	1,590	[4]
Leases [Member] | Originated Loans And Leases [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	1,062,161		900,371
Leases [Member] | Originated Loans And Leases [Member] | Performing Financing Receivable [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	1,060,953		898,781
Leases [Member] | Originated Loans And Leases [Member] | Nonperforming Financing Receivable [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	1,208	[4]	1,590	[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 Financing Receivable [Member] | Other Credit Exposure [Member]
Financing Receivable Recorded Investment [Line Items]
Credit Exposure	0		0
Leases [Member] | Purchased Loans And Leases [Member] | Nonperforming Financing Receivable [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.