Allowance for Loan and Lease Losses (Summary of Activity In Allowance for Loan and Lease Losses) (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Loans and Leases, Baseline for Meaurement			$ 500,000
Loans and Leases Evaluated for Impairment [Abstract]
Net loans and leases	18,886,204,000		18,564,999,000
Loan and Lease Acquired with Deteriorated Credit Quality [Abstract]
Allowance for loan and lease losses	205,553,000		204,466,000
PCI Loans
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	21,629,000	53,520,000
Provisions	(2,864,000)	(2,273,000)
Charge-offs	(1,146,000)	(6,254,000)
Recoveries	0	0
Ending balance	17,619,000	44,993,000
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Total allowance for loan and lease losses	17,619,000	44,993,000
Loan and Lease Acquired with Deteriorated Credit Quality [Abstract]
ALLL for loans and leases acquired with deteriorated credit quality	17,619,000		21,629,000
Loans and leases acquired with deteriorated credit quality	1,247,343,000		1,186,498,000
PCI Loans | Commercial | Construction and land development
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	150,000	1,320,000
Provisions	191,000	3,355,000
Charge-offs	0	(199,000)
Recoveries	0	0
Ending balance	341,000	4,476,000
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Total allowance for loan and lease losses	341,000	4,476,000
Loan and Lease Acquired with Deteriorated Credit Quality [Abstract]
ALLL for loans and leases acquired with deteriorated credit quality	341,000		150,000
Loans and leases acquired with deteriorated credit quality	70,049,000		78,079,000
PCI Loans | Commercial | Mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	10,135,000	29,906,000
Provisions	(925,000)	(3,386,000)
Charge-offs	(334,000)	(3,517,000)
Recoveries	0	0
Ending balance	8,876,000	23,003,000
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Total allowance for loan and lease losses	8,876,000	23,003,000
Loan and Lease Acquired with Deteriorated Credit Quality [Abstract]
ALLL for loans and leases acquired with deteriorated credit quality	8,876,000		10,135,000
Loans and leases acquired with deteriorated credit quality	653,846,000		577,518,000
PCI Loans | Commercial | Other commercial real estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	75,000	1,354,000
Provisions	119,000	(150,000)
Charge-offs	0	0
Recoveries	0	0
Ending balance	194,000	1,204,000
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Total allowance for loan and lease losses	194,000	1,204,000
Loan and Lease Acquired with Deteriorated Credit Quality [Abstract]
ALLL for loans and leases acquired with deteriorated credit quality	194,000		75,000
Loans and leases acquired with deteriorated credit quality	40,841,000		40,193,000
PCI Loans | Commercial | Commercial and industrial
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	1,240,000	5,275,000
Provisions	(1,031,000)	(336,000)
Charge-offs	(198,000)	(2,683,000)
Recoveries	0	0
Ending balance	11,000	2,256,000
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Total allowance for loan and lease losses	11,000	2,256,000
Loan and Lease Acquired with Deteriorated Credit Quality [Abstract]
ALLL for loans and leases acquired with deteriorated credit quality	11,000		1,240,000
Loans and leases acquired with deteriorated credit quality	24,134,000		27,254,000
PCI Loans | Noncommerical | Mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	5,820,000	11,802,000
Provisions	(863,000)	(2,300,000)
Charge-offs	(85,000)	262,000
Recoveries	0	0
Ending balance	4,872,000	9,764,000
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Total allowance for loan and lease losses	4,872,000	9,764,000
Loan and Lease Acquired with Deteriorated Credit Quality [Abstract]
ALLL for loans and leases acquired with deteriorated credit quality	4,872,000		5,820,000
Loans and leases acquired with deteriorated credit quality	380,490,000		382,339,000
PCI Loans | Noncommerical | Construction and land development
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	183,000	682,000
Provisions	(152,000)	(99,000)
Charge-offs	0	0
Recoveries	0	0
Ending balance	31,000	583,000
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Total allowance for loan and lease losses	31,000	583,000
Loan and Lease Acquired with Deteriorated Credit Quality [Abstract]
ALLL for loans and leases acquired with deteriorated credit quality	31,000		183,000
Loans and leases acquired with deteriorated credit quality	874,000		912,000
PCI Loans | Noncommerical | Revolving mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	3,999,000	2,959,000
Provisions	(655,000)	634,000
Charge-offs	(73,000)	(100,000)
Recoveries	0	0
Ending balance	3,271,000	3,493,000
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Total allowance for loan and lease losses	3,271,000	3,493,000
Loan and Lease Acquired with Deteriorated Credit Quality [Abstract]
ALLL for loans and leases acquired with deteriorated credit quality	3,271,000		3,999,000
Loans and leases acquired with deteriorated credit quality	70,363,000		74,109,000
PCI Loans | Noncommerical | Consumer and Other
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	27,000	222,000
Provisions	452,000	9,000
Charge-offs	(456,000)	(17,000)
Recoveries	0	0
Ending balance	23,000	214,000
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Total allowance for loan and lease losses	23,000	214,000
Loan and Lease Acquired with Deteriorated Credit Quality [Abstract]
ALLL for loans and leases acquired with deteriorated credit quality	23,000		27,000
Loans and leases acquired with deteriorated credit quality	6,746,000		6,094,000
Non-PCI Loans
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	182,837,000	179,874,000
Provisions	8,656,000	370,000
Charge-offs	(6,030,000)	(4,422,000)
Recoveries	2,471,000	2,127,000
Ending balance	187,934,000	177,949,000
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
ALLL for loans and leases individually evaluated for impairment	14,686,000		15,717,000
ALLL for loans and leases collectively evaluated for impairment	173,248,000		167,120,000
Total allowance for loan and lease losses	187,934,000	177,949,000
Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment	118,078,000		119,593,000
Loans and leases collectively evaluated for impairment	17,726,336,000		17,463,374,000
Net loans and leases	17,844,414,000		17,582,967,000
Non-PCI Loans | Commercial | Construction and land development
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	11,961,000	10,335,000
Provisions	1,103,000	1,885,000
Charge-offs	(18,000)	0
Recoveries	62,000	26,000
Ending balance	13,108,000	12,246,000
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
ALLL for loans and leases individually evaluated for impairment	182,000		92,000
ALLL for loans and leases collectively evaluated for impairment	12,926,000		11,869,000
Total allowance for loan and lease losses	13,108,000	12,246,000
Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment	2,972,000		1,620,000
Loans and leases collectively evaluated for impairment	605,584,000		548,948,000
Net loans and leases	608,556,000		550,568,000
Non-PCI Loans | Commercial | Mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	85,189,000	100,257,000
Provisions	(3,679,000)	(6,979,000)
Charge-offs	(233,000)	(168,000)
Recoveries	761,000	1,107,000
Ending balance	82,038,000	94,217,000
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
ALLL for loans and leases individually evaluated for impairment	7,494,000		8,610,000
ALLL for loans and leases collectively evaluated for impairment	74,544,000		76,579,000
Total allowance for loan and lease losses	82,038,000	94,217,000
Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment	77,291,000		82,803,000
Loans and leases collectively evaluated for impairment	7,514,454,000		7,470,145,000
Net loans and leases	7,591,745,000		7,552,948,000
Non-PCI Loans | Commercial | Other commercial real estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	732,000	1,009,000
Provisions	458,000	(74,000)
Charge-offs	(169,000)	0
Recoveries	10,000	10,000
Ending balance	1,031,000	945,000
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
ALLL for loans and leases individually evaluated for impairment	104,000		112,000
ALLL for loans and leases collectively evaluated for impairment	927,000		620,000
Total allowance for loan and lease losses	1,031,000	945,000
Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment	543,000		584,000
Loans and leases collectively evaluated for impairment	261,750,000		244,291,000
Net loans and leases	262,293,000		244,875,000
Non-PCI Loans | Commercial | Commercial and industrial
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	30,727,000	22,362,000
Provisions	7,546,000	1,976,000
Charge-offs	(1,713,000)	(496,000)
Recoveries	394,000	179,000
Ending balance	36,954,000	24,021,000
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
ALLL for loans and leases individually evaluated for impairment	2,809,000		1,743,000
ALLL for loans and leases collectively evaluated for impairment	34,145,000		28,984,000
Total allowance for loan and lease losses	36,954,000	24,021,000
Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment	13,969,000		11,040,000
Loans and leases collectively evaluated for impairment	2,058,445,000		1,977,894,000
Net loans and leases	2,072,414,000		1,988,934,000
Non-PCI Loans | Commercial | Lease financing
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	4,286,000	4,749,000
Provisions	11,000	(524,000)
Charge-offs	(15,000)	(58,000)
Recoveries	11,000	16,000
Ending balance	4,293,000	4,183,000
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
ALLL for loans and leases individually evaluated for impairment	236,000		150,000
ALLL for loans and leases collectively evaluated for impairment	4,057,000		4,136,000
Total allowance for loan and lease losses	4,293,000	4,183,000
Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment	1,492,000		623,000
Loans and leases collectively evaluated for impairment	602,245,000		571,293,000
Net loans and leases	603,737,000		571,916,000
Non-PCI Loans | Commercial | Other
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	3,184,000	190,000
Provisions	(218,000)	272,000
Charge-offs	0	(8,000)
Recoveries	15,000	0
Ending balance	2,981,000	454,000
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
ALLL for loans and leases individually evaluated for impairment	1,955,000		1,972,000
ALLL for loans and leases collectively evaluated for impairment	1,026,000		1,212,000
Total allowance for loan and lease losses	2,981,000	454,000
Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment	1,977,000		2,000,000
Loans and leases collectively evaluated for impairment	352,736,000		351,833,000
Net loans and leases	354,713,000		353,833,000
Non-PCI Loans | Noncommerical | Mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	10,661,000	10,511,000
Provisions	813,000	609,000
Charge-offs	(284,000)	(184,000)
Recoveries	138,000	8,000
Ending balance	11,328,000	10,944,000
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
ALLL for loans and leases individually evaluated for impairment	1,177,000		1,360,000
ALLL for loans and leases collectively evaluated for impairment	10,151,000		9,301,000
Total allowance for loan and lease losses	11,328,000	10,944,000
Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment	15,195,000		14,913,000
Loans and leases collectively evaluated for impairment	2,509,354,000		2,505,629,000
Net loans and leases	2,524,549,000		2,520,542,000
Non-PCI Loans | Noncommerical | Construction and land development
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	892,000	681,000
Provisions	118,000	577,000
Charge-offs	(22,000)	(71,000)
Recoveries	68,000	62,000
Ending balance	1,056,000	1,249,000
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
ALLL for loans and leases individually evaluated for impairment	90,000		71,000
ALLL for loans and leases collectively evaluated for impairment	966,000		821,000
Total allowance for loan and lease losses	1,056,000	1,249,000
Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment	733,000		1,340,000
Loans and leases collectively evaluated for impairment	169,475,000		118,757,000
Net loans and leases	170,208,000		120,097,000
Non-PCI Loans | Noncommerical | Revolving mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	18,650,000	16,239,000
Provisions	(462,000)	1,353,000
Charge-offs	(793,000)	(1,260,000)
Recoveries	134,000	76,000
Ending balance	17,529,000	16,408,000
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
ALLL for loans and leases individually evaluated for impairment	108,000		1,052,000
ALLL for loans and leases collectively evaluated for impairment	17,421,000		17,598,000
Total allowance for loan and lease losses	17,529,000	16,408,000
Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment	2,922,000		3,675,000
Loans and leases collectively evaluated for impairment	2,525,335,000		2,558,125,000
Net loans and leases	2,528,257,000		2,561,800,000
Non-PCI Loans | Noncommerical | Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	16,555,000	13,541,000
Provisions	2,966,000	1,275,000
Charge-offs	(2,783,000)	(2,177,000)
Recoveries	878,000	643,000
Ending balance	17,616,000	13,282,000
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
ALLL for loans and leases individually evaluated for impairment	531,000		555,000
ALLL for loans and leases collectively evaluated for impairment	17,085,000		16,000,000
Total allowance for loan and lease losses	17,616,000	13,282,000
Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment	984,000		995,000
Loans and leases collectively evaluated for impairment	1,126,958,000		1,116,459,000
Net loans and leases	$ 1,127,942,000		$ 1,117,454,000