Loans and Leases (Composition of the Loans and Leases Outstanding By Credit Quality Indicator) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
PCI loans	$ 1,247,343	$ 1,186,498	$ 1,270,818	$ 1,029,426
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	11,493,458	11,263,074
PCI loans	791,756	726,123
Commercial | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	608,556	550,568
PCI loans	70,049	78,079
Commercial | Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	7,591,745	7,552,948
PCI loans	653,846	577,518
Commercial | Other commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	262,293	244,875
PCI loans	40,841	40,193
Commercial | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	2,072,414	1,988,934
PCI loans	24,134	27,254
Commercial | Lease financing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	603,737	571,916
Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	354,713	353,833
PCI loans	2,886	3,079
Commercial | Pass
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	11,070,735	10,825,323
PCI loans	371,135	342,172
Commercial | Pass | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	590,298	525,711
PCI loans	13,832	13,514
Commercial | Pass | Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	7,341,243	7,284,714
PCI loans	333,368	300,187
Commercial | Pass | Other commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	260,592	242,053
PCI loans	9,727	11,033
Commercial | Pass | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	1,931,078	1,859,415
PCI loans	13,525	16,637
Commercial | Pass | Lease financing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	597,464	564,319
Commercial | Pass | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	350,060	349,111
PCI loans	683	801
Commercial | Special Mention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	157,884	182,453
PCI loans	141,884	125,195
Commercial | Special Mention | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	15,679	20,025
PCI loans	4,287	6,063
Commercial | Special Mention | Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	115,411	129,247
PCI loans	118,209	98,724
Commercial | Special Mention | Other commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	501	909
PCI loans	16,425	16,271
Commercial | Special Mention | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	21,771	27,683
PCI loans	2,963	4,137
Commercial | Special Mention | Lease financing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	2,609	3,205
Commercial | Special Mention | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	1,913	1,384
PCI loans	0	0
Commercial | Substandard
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	149,792	157,333
PCI loans	259,917	247,138
Commercial | Substandard | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	2,291	4,720
PCI loans	44,663	53,739
Commercial | Substandard | Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	131,672	134,677
PCI loans	193,435	171,920
Commercial | Substandard | Other commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	1,049	1,765
PCI loans	12,948	12,889
Commercial | Substandard | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	8,806	8,878
PCI loans	6,739	6,312
Commercial | Substandard | Lease financing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	3,284	3,955
Commercial | Substandard | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	2,690	3,338
PCI loans	2,132	2,278
Commercial | Doubtful
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	6,770	2,895
PCI loans	15,437	9,241
Commercial | Doubtful | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	0	0
PCI loans	4,656	2,809
Commercial | Doubtful | Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	2,039	2,366
PCI loans	8,456	6,302
Commercial | Doubtful | Other commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	0	0
PCI loans	1,741	0
Commercial | Doubtful | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	4,402	164
PCI loans	513	130
Commercial | Doubtful | Lease financing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	329	365
Commercial | Doubtful | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	0	0
PCI loans	71	0
Commercial | Ungraded
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	108,277	95,070
PCI loans	3,383	2,377
Commercial | Ungraded | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	288	112
PCI loans	2,611	1,954
Commercial | Ungraded | Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	1,380	1,944
PCI loans	378	385
Commercial | Ungraded | Other commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	151	148
PCI loans	0	0
Commercial | Ungraded | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	106,357	92,794
PCI loans	394	38
Commercial | Ungraded | Lease financing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	51	72
Commercial | Ungraded | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	50	0
PCI loans	0	0
Noncommerical
Accounts, Notes, Loans and Financing Receivable [Line Items]
PCI loans	455,587	460,375
Noncommerical | Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
PCI loans	380,490	382,340
Noncommerical | Revolving mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
PCI loans	70,363	74,109
Noncommerical | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
PCI loans	874	912
Noncommerical | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
PCI loans	3,860	3,014
Purchased credit-impaired | Noncommerical
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	388,349	398,225
PCI loans	455,587	460,375
30-59 Days Past Due	21,672	12,984
60-89 Days Past Due	7,836	10,443
90 Days or Greater	37,730	38,723
Purchased credit-impaired | Noncommerical | Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	320,607	326,589
PCI loans	380,490	382,340
30-59 Days Past Due	18,742	11,432
60-89 Days Past Due	6,804	10,073
90 Days or Greater	34,337	34,246
Purchased credit-impaired | Noncommerical | Revolving mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	63,579	68,548
PCI loans	70,363	74,109
30-59 Days Past Due	2,800	1,405
60-89 Days Past Due	1,019	345
90 Days or Greater	2,965	3,811
Purchased credit-impaired | Noncommerical | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	592	506
PCI loans	874	912
30-59 Days Past Due	0	0
60-89 Days Past Due	0	0
90 Days or Greater	282	406
Purchased credit-impaired | Noncommerical | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	3,571	2,582
PCI loans	3,860	3,014
30-59 Days Past Due	130	147
60-89 Days Past Due	13	25
90 Days or Greater	146	260
Non-PCI Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	17,844,414	17,582,967
Current	17,732,161	17,481,500
30-59 Days Past Due	71,450	57,321
60-89 Days Past Due	15,735	19,548
90 Days or Greater	25,068	24,598
Non-PCI Loans | Commercial | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	608,556	550,568
Current	604,091	547,766
30-59 Days Past Due	2,709	1,796
60-89 Days Past Due	712	621
90 Days or Greater	1,044	385
Non-PCI Loans | Commercial | Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	7,591,745	7,552,948
Current	7,554,745	7,528,738
30-59 Days Past Due	22,635	11,367
60-89 Days Past Due	5,920	4,782
90 Days or Greater	8,445	8,061
Non-PCI Loans | Commercial | Other commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	262,293	244,875
Current	261,456	244,497
30-59 Days Past Due	583	206
60-89 Days Past Due	58	70
90 Days or Greater	196	102
Non-PCI Loans | Commercial | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	2,072,414	1,988,934
Current	2,063,830	1,984,168
30-59 Days Past Due	6,290	2,843
60-89 Days Past Due	1,724	1,545
90 Days or Greater	570	378
Non-PCI Loans | Commercial | Lease financing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	603,737	571,916
Current	603,250	570,275
30-59 Days Past Due	476	1,631
60-89 Days Past Due	11	8
90 Days or Greater	0	2
Non-PCI Loans | Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	354,713	353,833
Current	354,135	351,721
30-59 Days Past Due	380	146
60-89 Days Past Due	65	1,966
90 Days or Greater	133	0
Non-PCI Loans | Noncommerical
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	6,350,956	6,319,893
Current	6,290,654	6,254,335
30-59 Days Past Due	38,377	39,332
60-89 Days Past Due	7,245	10,556
90 Days or Greater	14,680	15,670
Non-PCI Loans | Noncommerical | Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	2,524,549	2,520,542
Current	2,490,453	2,482,281
30-59 Days Past Due	21,844	23,288
60-89 Days Past Due	2,896	6,018
90 Days or Greater	9,356	8,955
Non-PCI Loans | Noncommerical | Revolving mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	2,528,257	2,561,800
Current	2,510,879	2,542,807
30-59 Days Past Due	10,288	11,097
60-89 Days Past Due	2,794	2,433
90 Days or Greater	4,296	5,463
Non-PCI Loans | Noncommerical | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	170,208	120,097
Current	168,199	119,094
30-59 Days Past Due	2,009	370
60-89 Days Past Due	0	486
90 Days or Greater	0	147
Non-PCI Loans | Noncommerical | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, not acquired in a transfer accounted for as debt securities	1,127,942	1,117,454
Current	1,121,123	1,110,153
30-59 Days Past Due	4,236	4,577
60-89 Days Past Due	1,555	1,619
90 Days or Greater	$ 1,028	$ 1,105