Allowance For Loan & Lease Losses (Allowance For Credit Losses And Recorded Investment In Financing Receivables) (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance For Credit Losses, Beginning Balance	$ 144,483,000	$ 178,594,000	$ 157,608,000	$ 184,020,000
Charge-Offs	(20,969,000)	(25,934,000)	(50,311,000)	(67,465,000)
Recoveries	4,356,000	9,080,000	12,809,000	21,185,000
Transfer For Loans Designated As Held For Sale	0		(1,236,000)
Provision	9,000,000	5,000,000	18,000,000	29,000,000
Allowance For Credit Losses, Ending Balance	136,870,000	166,740,000	136,870,000	166,740,000
Individually evaluated for impairment	12,394,000	15,305,000	12,394,000	15,305,000
Collectively evaluated for impairment	124,476,000	151,435,000	124,476,000	151,435,000
Financing Receivables, Ending Balance	13,425,721,000	13,376,454,000	13,425,721,000	13,376,454,000
Financing receivables, Individually evaluated for impairment, Ending Balance	208,147,000	264,427,000	208,147,000	264,427,000
Financing receivables, Collectively evaluated for impairment, Ending Balance	13,217,574,000	13,112,027,000	13,217,574,000	13,112,027,000
Originated Loans And Leases [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Individually evaluated for impairment	10,780,000	11,718,000	10,780,000	11,718,000
Collectively evaluated for impairment	124,476,000	151,435,000	124,476,000	151,435,000
Financing receivables, Individually evaluated for impairment, Ending Balance	101,312,000	125,924,000	101,312,000	125,924,000
Financing receivables, Collectively evaluated for impairment, Ending Balance	11,891,857,000	11,496,539,000	11,891,857,000	11,496,539,000
Purchased Loans And Leases [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Individually evaluated for impairment	1,614,000	3,587,000	1,614,000	3,587,000
Collectively evaluated for impairment	0	0	0	0
Financing receivables, Individually evaluated for impairment, Ending Balance	106,835,000	138,503,000	106,835,000	138,503,000
Financing receivables, Collectively evaluated for impairment, Ending Balance	1,325,717,000	1,615,488,000	1,325,717,000	1,615,488,000
Commercial, Financial, And Agricultural [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance For Credit Losses, Beginning Balance	41,401,000	30,237,000	40,590,000	30,207,000
Charge-Offs	(9,398,000)	(5,892,000)	(23,006,000)	(26,758,000)
Recoveries	1,329,000	2,161,000	4,481,000	6,197,000
Transfer For Loans Designated As Held For Sale	0		0
Provision	12,540,000	4,491,000	23,807,000	21,351,000
Allowance For Credit Losses, Ending Balance	45,872,000	30,997,000	45,872,000	30,997,000
Individually evaluated for impairment	6,115,000	3,129,000	6,115,000	3,129,000
Collectively evaluated for impairment	39,757,000	26,916,000	39,757,000	26,916,000
Financing Receivables, Ending Balance	2,362,201,000	2,273,735,000	2,362,201,000	2,273,735,000
Financing receivables, Individually evaluated for impairment, Ending Balance	26,779,000	28,435,000	26,779,000	28,435,000
Financing receivables, Collectively evaluated for impairment, Ending Balance	2,335,422,000	2,245,300,000	2,335,422,000	2,245,300,000
Commercial, Financial, And Agricultural [Member] | Originated Loans And Leases [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Individually evaluated for impairment	6,089,000	1,853,000	6,089,000	1,853,000
Collectively evaluated for impairment	39,757,000	26,916,000	39,757,000	26,916,000
Financing receivables, Individually evaluated for impairment, Ending Balance	20,435,000	12,236,000	20,435,000	12,236,000
Financing receivables, Collectively evaluated for impairment, Ending Balance	2,209,028,000	2,133,682,000	2,209,028,000	2,133,682,000
Commercial, Financial, And Agricultural [Member] | Purchased Loans And Leases [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Individually evaluated for impairment	26,000	1,276,000	26,000	1,276,000
Collectively evaluated for impairment	0	0	0	0
Financing receivables, Individually evaluated for impairment, Ending Balance	6,344,000	16,199,000	6,344,000	16,199,000
Financing receivables, Collectively evaluated for impairment, Ending Balance	126,394,000	111,618,000	126,394,000	111,618,000
Real Estate - Construction [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance For Credit Losses, Beginning Balance	18,180,000	23,568,000	26,189,000	25,171,000
Charge-Offs	(1,038,000)	(8,103,000)	(1,668,000)	(14,036,000)
Recoveries	262,000	1,599,000	1,440,000	3,786,000
Transfer For Loans Designated As Held For Sale	0		0
Provision	(3,606,000)	6,910,000	(12,163,000)	9,053,000
Allowance For Credit Losses, Ending Balance	13,798,000	23,974,000	13,798,000	23,974,000
Individually evaluated for impairment	656,000	2,105,000	656,000	2,105,000
Collectively evaluated for impairment	13,142,000	21,839,000	13,142,000	21,839,000
Financing Receivables, Ending Balance	817,492,000	765,246,000	817,492,000	765,246,000
Financing receivables, Individually evaluated for impairment, Ending Balance	10,650,000	26,225,000	10,650,000	26,225,000
Financing receivables, Collectively evaluated for impairment, Ending Balance	806,842,000	739,021,000	806,842,000	739,021,000
Real Estate - Construction [Member] | Originated Loans And Leases [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Individually evaluated for impairment	656,000	1,762,000	656,000	1,762,000
Collectively evaluated for impairment	13,142,000	21,839,000	13,142,000	21,839,000
Financing receivables, Individually evaluated for impairment, Ending Balance	3,307,000	13,905,000	3,307,000	13,905,000
Financing receivables, Collectively evaluated for impairment, Ending Balance	761,491,000	660,317,000	761,491,000	660,317,000
Real Estate - Construction [Member] | Purchased Loans And Leases [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Individually evaluated for impairment	0	343,000	0	343,000
Collectively evaluated for impairment	0	0	0	0
Financing receivables, Individually evaluated for impairment, Ending Balance	7,343,000	12,320,000	7,343,000	12,320,000
Financing receivables, Collectively evaluated for impairment, Ending Balance	45,351,000	78,704,000	45,351,000	78,704,000
Real Estate Secured - Residential [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance For Credit Losses, Beginning Balance	21,376,000	37,716,000	24,076,000	41,276,000
Charge-Offs	(3,020,000)	(4,151,000)	(10,140,000)	(9,771,000)
Recoveries	471,000	627,000	2,342,000	1,879,000
Transfer For Loans Designated As Held For Sale	0		0
Provision	2,264,000	(4,995,000)	4,813,000	(4,187,000)
Allowance For Credit Losses, Ending Balance	21,091,000	29,197,000	21,091,000	29,197,000
Individually evaluated for impairment	3,209,000	2,615,000	3,209,000	2,615,000
Collectively evaluated for impairment	17,882,000	26,596,000	17,882,000	26,596,000
Financing Receivables, Ending Balance	4,172,943,000	4,145,522,000	4,172,943,000	4,145,522,000
Financing receivables, Individually evaluated for impairment, Ending Balance	43,805,000	63,184,000	43,805,000	63,184,000
Financing receivables, Collectively evaluated for impairment, Ending Balance	4,129,138,000	4,082,338,000	4,129,138,000	4,082,338,000
Real Estate Secured - Residential [Member] | Originated Loans And Leases [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Individually evaluated for impairment	2,076,000	1,440,000	2,076,000	1,440,000
Collectively evaluated for impairment	17,882,000	26,596,000	17,882,000	26,596,000
Financing receivables, Individually evaluated for impairment, Ending Balance	23,689,000	33,910,000	23,689,000	33,910,000
Financing receivables, Collectively evaluated for impairment, Ending Balance	3,577,869,000	3,317,817,000	3,577,869,000	3,317,817,000
Real Estate Secured - Residential [Member] | Purchased Loans And Leases [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Individually evaluated for impairment	1,133,000	1,175,000	1,133,000	1,175,000
Collectively evaluated for impairment	0	0	0	0
Financing receivables, Individually evaluated for impairment, Ending Balance	20,116,000	29,274,000	20,116,000	29,274,000
Financing receivables, Collectively evaluated for impairment, Ending Balance	551,269,000	764,521,000	551,269,000	764,521,000
Real Estate Secured - Commercial [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance For Credit Losses, Beginning Balance	46,952,000	68,827,000	48,261,000	70,053,000
Charge-Offs	(5,144,000)	(6,043,000)	(8,828,000)	(11,488,000)
Recoveries	1,317,000	4,036,000	2,137,000	6,841,000
Transfer For Loans Designated As Held For Sale	0		0
Provision	(1,359,000)	(1,602,000)	196,000	(188,000)
Allowance For Credit Losses, Ending Balance	41,766,000	65,218,000	41,766,000	65,218,000
Individually evaluated for impairment	2,300,000	7,406,000	2,300,000	7,406,000
Collectively evaluated for impairment	39,466,000	58,772,000	39,466,000	58,772,000
Financing Receivables, Ending Balance	4,016,635,000	4,109,329,000	4,016,635,000	4,109,329,000
Financing receivables, Individually evaluated for impairment, Ending Balance	125,862,000	144,589,000	125,862,000	144,589,000
Financing receivables, Collectively evaluated for impairment, Ending Balance	3,890,773,000	3,964,740,000	3,890,773,000	3,964,740,000
Real Estate Secured - Commercial [Member] | Originated Loans And Leases [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Individually evaluated for impairment	1,845,000	6,614,000	1,845,000	6,614,000
Collectively evaluated for impairment	39,466,000	58,772,000	39,466,000	58,772,000
Financing receivables, Individually evaluated for impairment, Ending Balance	52,832,000	64,143,000	52,832,000	64,143,000
Financing receivables, Collectively evaluated for impairment, Ending Balance	3,293,267,000	3,311,119,000	3,293,267,000	3,311,119,000
Real Estate Secured - Commercial [Member] | Purchased Loans And Leases [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Individually evaluated for impairment	455,000	792,000	455,000	792,000
Collectively evaluated for impairment	0	0	0	0
Financing receivables, Individually evaluated for impairment, Ending Balance	73,030,000	80,446,000	73,030,000	80,446,000
Financing receivables, Collectively evaluated for impairment, Ending Balance	597,506,000	653,621,000	597,506,000	653,621,000
Consumer [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance For Credit Losses, Beginning Balance	1,276,000	3,155,000	2,266,000	3,722,000
Charge-Offs	(891,000)	(1,051,000)	(3,470,000)	(2,397,000)
Recoveries	277,000	325,000	988,000	886,000
Transfer For Loans Designated As Held For Sale	0		(1,236,000)
Provision	636,000	(479,000)	2,750,000	(261,000)
Allowance For Credit Losses, Ending Balance	1,298,000	1,950,000	1,298,000	1,950,000
Individually evaluated for impairment	114,000	50,000	114,000	50,000
Collectively evaluated for impairment	1,184,000	1,908,000	1,184,000	1,908,000
Financing Receivables, Ending Balance	730,687,000	935,117,000	730,687,000	935,117,000
Financing receivables, Individually evaluated for impairment, Ending Balance	1,051,000	1,994,000	1,051,000	1,994,000
Financing receivables, Collectively evaluated for impairment, Ending Balance	729,636,000	933,123,000	729,636,000	933,123,000
Consumer [Member] | Originated Loans And Leases [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Individually evaluated for impairment	114,000	49,000	114,000	49,000
Collectively evaluated for impairment	1,184,000	1,908,000	1,184,000	1,908,000
Financing receivables, Individually evaluated for impairment, Ending Balance	1,049,000	1,730,000	1,049,000	1,730,000
Financing receivables, Collectively evaluated for impairment, Ending Balance	724,439,000	926,099,000	724,439,000	926,099,000
Consumer [Member] | Purchased Loans And Leases [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Individually evaluated for impairment	0	1,000	0	1,000
Collectively evaluated for impairment	0	0	0	0
Financing receivables, Individually evaluated for impairment, Ending Balance	2,000	264,000	2,000	264,000
Financing receivables, Collectively evaluated for impairment, Ending Balance	5,197,000	7,024,000	5,197,000	7,024,000
Leases [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance For Credit Losses, Beginning Balance	13,875,000	14,750,000	15,259,000	13,341,000
Charge-Offs	(1,478,000)	(694,000)	(3,199,000)	(3,015,000)
Recoveries	700,000	332,000	1,421,000	1,596,000
Transfer For Loans Designated As Held For Sale	0		0
Provision	(228,000)	640,000	(612,000)	3,106,000
Allowance For Credit Losses, Ending Balance	12,869,000	15,028,000	12,869,000	15,028,000
Individually evaluated for impairment	0	0	0	0
Collectively evaluated for impairment	12,869,000	15,028,000	12,869,000	15,028,000
Financing Receivables, Ending Balance	1,325,763,000	1,147,505,000	1,325,763,000	1,147,505,000
Financing receivables, Individually evaluated for impairment, Ending Balance	0	0	0	0
Financing receivables, Collectively evaluated for impairment, Ending Balance	1,325,763,000	1,147,505,000	1,325,763,000	1,147,505,000
Leases [Member] | Originated Loans And Leases [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Individually evaluated for impairment	0	0	0	0
Collectively evaluated for impairment	12,869,000	15,028,000	12,869,000	15,028,000
Financing receivables, Individually evaluated for impairment, Ending Balance	0	0	0	0
Financing receivables, Collectively evaluated for impairment, Ending Balance	1,325,763,000	1,147,505,000	1,325,763,000	1,147,505,000
Leases [Member] | Purchased Loans And Leases [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Individually evaluated for impairment	0	0	0	0
Collectively evaluated for impairment	0	0	0	0
Financing receivables, Individually evaluated for impairment, Ending Balance	0	0	0	0
Financing receivables, Collectively evaluated for impairment, Ending Balance	0	0	0	0
Unallocated [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance For Credit Losses, Beginning Balance	1,423,000	341,000	967,000	250,000
Charge-Offs	0	0	0	0
Recoveries	0	0	0	0
Transfer For Loans Designated As Held For Sale	0		0
Provision	(1,247,000)	35,000	(791,000)	126,000
Allowance For Credit Losses, Ending Balance	176,000	376,000	176,000	376,000
Collectively evaluated for impairment	176,000	376,000	176,000	376,000
Unallocated [Member] | Originated Loans And Leases [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Collectively evaluated for impairment	176,000	376,000	176,000	376,000
Unallocated [Member] | Purchased Loans And Leases [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Collectively evaluated for impairment	$ 0	$ 0	$ 0	$ 0