Loans and Leases (Age Analysis of Past Due Financing Receivables) (Detail) (USD $)	Jun. 30, 2014	Dec. 31, 2013
Financing Receivables That Are Accruing [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
30-59 Days Past Due	$ 18,336,000	$ 57,234,000
60-89 Days Past Due	19,103,000	11,389,000
90 Days and Greater	9,190,000	9,757,000
Total Past Due	46,629,000	78,380,000
Current	13,514,915,000	13,396,891,000
Total Financing Receivables, Accruing	13,561,544,000	13,475,271,000
Financing Receivables That Are Accruing [Member] | Originated Loans And Leases [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
30-59 Days Past Due	16,051,000	46,031,000
60-89 Days Past Due	17,055,000	9,381,000
90 Days and Greater	4,518,000	7,302,000
Total Past Due	37,624,000	62,714,000
Current	12,035,233,000	11,787,333,000
Total Financing Receivables, Accruing	12,072,857,000	11,850,047,000
Financing Receivables That Are Accruing [Member] | Purchased Loans And Leases [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
30-59 Days Past Due	2,285,000	11,203,000
60-89 Days Past Due	2,048,000	2,008,000
90 Days and Greater	4,672,000	2,455,000
Total Past Due	9,005,000	15,666,000
Current	1,479,682,000	1,609,558,000
Total Financing Receivables, Accruing	1,488,687,000	1,625,224,000
Financing Receivables That Are Accruing [Member] | Commercial, Financial, And Agricultural [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
30-59 Days Past Due	1,297,000	3,640,000
60-89 Days Past Due	468,000	518,000
90 Days and Greater	20,000	127,000
Total Past Due	1,785,000	4,285,000
Current	2,402,354,000	2,373,735,000
Total Financing Receivables, Accruing	2,404,139,000	2,378,020,000
Financing Receivables That Are Accruing [Member] | Real Estate - Construction [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
30-59 Days Past Due	183,000	1,631,000
60-89 Days Past Due	745,000	903,000
90 Days and Greater	692,000	418,000
Total Past Due	1,620,000	2,952,000
Current	739,133,000	719,695,000
Total Financing Receivables, Accruing	740,753,000	722,647,000
Financing Receivables That Are Accruing [Member] | Real Estate Secured - Residential [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
30-59 Days Past Due	8,296,000	27,441,000
60-89 Days Past Due	3,709,000	6,223,000
90 Days and Greater	6,018,000	7,274,000
Total Past Due	18,023,000	40,938,000
Current	4,136,079,000	4,140,127,000
Total Financing Receivables, Accruing	4,154,102,000	4,181,065,000
Financing Receivables That Are Accruing [Member] | Real Estate Secured - Commercial [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
30-59 Days Past Due	2,544,000	11,583,000
60-89 Days Past Due	12,850,000	1,840,000
90 Days and Greater	1,903,000	667,000
Total Past Due	17,297,000	14,090,000
Current	3,983,006,000	4,008,579,000
Total Financing Receivables, Accruing	4,000,303,000	4,022,669,000
Financing Receivables That Are Accruing [Member] | Consumer [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
30-59 Days Past Due	5,245,000	8,664,000
60-89 Days Past Due	1,015,000	1,537,000
90 Days and Greater	291,000	983,000
Total Past Due	6,551,000	11,184,000
Current	956,024,000	941,769,000
Total Financing Receivables, Accruing	962,575,000	952,953,000
Financing Receivables That Are Accruing [Member] | Leases [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
30-59 Days Past Due	771,000	4,275,000
60-89 Days Past Due	316,000	368,000
90 Days and Greater	266,000	288,000
Total Past Due	1,353,000	4,931,000
Current	1,298,319,000	1,212,986,000
Total Financing Receivables, Accruing	1,299,672,000	1,217,917,000
Financing Receivables That Are Nonaccruing [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
30-59 Days Past Due	2,039,000	8,937,000
60-89 Days Past Due	2,260,000	5,890,000
90 Days and Greater	60,230,000	46,788,000
Total Past Due	64,529,000	61,615,000
Current	41,080,000	39,200,000
Total Financing Receivables, Nonaccruing	105,609,000	100,815,000
Financing Receivables That Are Nonaccruing [Member] | Originated Loans And Leases [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
30-59 Days Past Due	1,550,000	8,205,000
60-89 Days Past Due	2,152,000	3,806,000
90 Days and Greater	49,750,000	39,553,000
Total Past Due	53,452,000	51,564,000
Current	32,965,000	29,335,000
Total Financing Receivables, Nonaccruing	86,417,000	80,899,000
Financing Receivables That Are Nonaccruing [Member] | Purchased Loans And Leases [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
30-59 Days Past Due	489,000	732,000
60-89 Days Past Due	108,000	2,084,000
90 Days and Greater	10,480,000	7,235,000
Total Past Due	11,077,000	10,051,000
Current	8,115,000	9,865,000
Total Financing Receivables, Nonaccruing	19,192,000	19,916,000
Financing Receivables That Are Nonaccruing [Member] | Commercial, Financial, And Agricultural [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
30-59 Days Past Due	95,000	4,832,000
60-89 Days Past Due	1,436,000	855,000
90 Days and Greater	9,246,000	4,850,000
Total Past Due	10,777,000	10,537,000
Current	8,015,000	6,290,000
Total Financing Receivables, Nonaccruing	18,792,000	16,827,000
Financing Receivables That Are Nonaccruing [Member] | Real Estate - Construction [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
30-59 Days Past Due	0	2,176,000
60-89 Days Past Due	0	788,000
90 Days and Greater	3,604,000	5,320,000
Total Past Due	3,604,000	8,284,000
Current	3,824,000	4,946,000
Total Financing Receivables, Nonaccruing	7,428,000	13,230,000
Financing Receivables That Are Nonaccruing [Member] | Real Estate Secured - Residential [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
30-59 Days Past Due	79,000	609,000
60-89 Days Past Due	544,000	497,000
90 Days and Greater	16,819,000	16,518,000
Total Past Due	17,442,000	17,624,000
Current	7,298,000	5,741,000
Total Financing Receivables, Nonaccruing	24,740,000	23,365,000
Financing Receivables That Are Nonaccruing [Member] | Real Estate Secured - Commercial [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
30-59 Days Past Due	1,865,000	1,320,000
60-89 Days Past Due	98,000	3,551,000
90 Days and Greater	30,527,000	19,952,000
Total Past Due	32,490,000	24,823,000
Current	21,197,000	21,324,000
Total Financing Receivables, Nonaccruing	53,687,000	46,147,000
Financing Receivables That Are Nonaccruing [Member] | Consumer [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
30-59 Days Past Due	0	0
60-89 Days Past Due	0	0
90 Days and Greater	10,000	0
Total Past Due	10,000	0
Current	33,000	47,000
Total Financing Receivables, Nonaccruing	43,000	47,000
Financing Receivables That Are Nonaccruing [Member] | Leases [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
30-59 Days Past Due	0	0
60-89 Days Past Due	182,000	199,000
90 Days and Greater	24,000	148,000
Total Past Due	206,000	347,000
Current	713,000	852,000
Total Financing Receivables, Nonaccruing	$ 919,000	$ 1,199,000