Allowance for Loan and Lease Losses (Allocation of Allowance for Loan and Lease Losses) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	$ 1,788,136	$ 1,754,882	$ 1,788,136	$ 1,754,882
Allowance for loan and lease losses	205,463		205,463		$ 204,466
Loans and Leases Receivable, Net Amount	19,650,343		19,650,343		18,564,999
PCI Loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Acquired loans which have adverse change in expected cash flows	514,800		514,800		285,600
Provision for Loan, Lease, and Other Losses	2,769	(197)	(1,370)	(11,999)
Provision Expense And Accretion Income Reclassification	3,900
Financing Receivable, Allowance for Credit Losses, Write-downs	680	3,334	2,702	15,721
Recoveries	0	0	0	0
PCI Loans | Commercial | Construction and land development
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for Loan, Lease, and Other Losses	632	(1,815)	1,148	1,463
Financing Receivable, Allowance for Credit Losses, Write-downs	0	1,633	97	2,428
Recoveries	0	0	0	0
PCI Loans | Commercial | Mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for Loan, Lease, and Other Losses	2,187	(2,374)	(803)	(6,946)
Financing Receivable, Allowance for Credit Losses, Write-downs	48	2,357	765	10,376
Recoveries	0	0	0	0
PCI Loans | Commercial | Other commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for Loan, Lease, and Other Losses	$ 235	(435)	229	(1,382)
Financing Receivable, Allowance for Credit Losses, Write-downs		(106)	0	(106)
Recoveries	$ 0	0	0	0
PCI Loans | Commercial | Commercial and industrial
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for Loan, Lease, and Other Losses	118	182	(514)	(1,883)
Financing Receivable, Allowance for Credit Losses, Write-downs	39	(839)	324	1,996
Recoveries	0	0	0	0
PCI Loans | Noncommerical | Construction and land development
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for Loan, Lease, and Other Losses	0	239	(183)	(443)
Financing Receivable, Allowance for Credit Losses, Write-downs	0	83	0	83
Recoveries	0	0	0	0
PCI Loans | Noncommerical | Consumer and Other
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for Loan, Lease, and Other Losses	29	(80)	650	(21)
Financing Receivable, Allowance for Credit Losses, Write-downs	1	17	463	41
Recoveries	0	0	0	0
PCI Loans | Noncommerical | Mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for Loan, Lease, and Other Losses	(281)	187	21	(4,289)
Financing Receivable, Allowance for Credit Losses, Write-downs	15	188	295	421
Recoveries	0	0	0	0
PCI Loans | Noncommerical | Revolving mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for Loan, Lease, and Other Losses	(151)	3,899	(1,918)	1,502
Financing Receivable, Allowance for Credit Losses, Write-downs	577	1	758	482
Recoveries	0	0	0	0
Non-PCI Loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Total impaired noncovered loans and leases	142,962		142,962		119,593
Unpaid principal balance	159,307		159,307		133,466
Impaired Financing Receivable, Related Allowance	8,491		8,491		15,717
ALLL for loans and leases individually evaluated for impairment	8,491		8,491		15,717
Impaired Financing Receivable, with Related Allowance, Recorded Investment	67,619		67,619		87,007
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	75,343		75,343		32,586
Financing Receivable, Individually Evaluated for Impairment	142,962		142,962		119,593
Average balance	151,108	128,431	132,864	128,357
Interest income recognized	1,218	1,139	3,528	3,782
Provision for Loan, Lease, and Other Losses	(2,662)	1,734	14,988	4,334
Financing Receivable, Allowance for Credit Losses, Write-downs	5,018	5,387	17,098	14,578
Recoveries	2,737	1,843	7,179	5,475
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	179,415		179,415		167,120
Financing Receivable, Collectively Evaluated for Impairment	18,668,780		18,668,780		17,463,374
Loans and Leases Receivable, Net Amount	18,811,742		18,811,742		17,582,967
Non-PCI Loans | Commercial | Construction and land development
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	4,594		4,594		6,945
ALLL for loans and leases individually evaluated for impairment	417		417		92
Impaired Financing Receivable, with Related Allowance, Recorded Investment	1,799		1,799		996
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	1,395		1,395		624
Financing Receivable, Individually Evaluated for Impairment	3,194		3,194		1,620
Average balance	3,257	2,296	3,148	1,701
Interest income recognized	37	26	107	57
Provision for Loan, Lease, and Other Losses	1,189	1,469	2,380	2,219
Financing Receivable, Allowance for Credit Losses, Write-downs	336	0	575	0
Recoveries	129	15	295	46
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	13,644		13,644		11,869
Financing Receivable, Collectively Evaluated for Impairment	560,732		560,732		491,513
Loans and Leases Receivable, Net Amount	563,926		563,926		493,133
Non-PCI Loans | Commercial | Mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	100,914		100,914		87,702
ALLL for loans and leases individually evaluated for impairment	4,007		4,007		8,610
Impaired Financing Receivable, with Related Allowance, Recorded Investment	42,562		42,562		57,324
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	50,183		50,183		25,479
Financing Receivable, Individually Evaluated for Impairment	92,745		92,745		82,803
Average balance	99,613	90,318	88,614	86,131
Interest income recognized	803	806	2,405	2,522
Provision for Loan, Lease, and Other Losses	(5,664)	(8,082)	(11,221)	(17,021)
Financing Receivable, Allowance for Credit Losses, Write-downs	411	277	691	718
Recoveries	794	476	1,878	1,728
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	71,148		71,148		76,579
Financing Receivable, Collectively Evaluated for Impairment	7,984,201		7,984,201		7,470,145
Loans and Leases Receivable, Net Amount	8,076,946		8,076,946		7,552,948
Non-PCI Loans | Commercial | Other commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	868		868		913
ALLL for loans and leases individually evaluated for impairment	295		295		112
Impaired Financing Receivable, with Related Allowance, Recorded Investment	312		312		112
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	124		124		472
Financing Receivable, Individually Evaluated for Impairment	436		436		584
Average balance	539	1,980	498	2,474
Interest income recognized	6	7	7	67
Provision for Loan, Lease, and Other Losses	291	61	522	(167)
Financing Receivable, Allowance for Credit Losses, Write-downs	0	0	178	0
Recoveries	15	8	34	33
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	815		815		620
Financing Receivable, Collectively Evaluated for Impairment	316,488		316,488		244,291
Loans and Leases Receivable, Net Amount	316,924		316,924		244,875
Non-PCI Loans | Commercial | Commercial and industrial
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	19,608		19,608		12,197
ALLL for loans and leases individually evaluated for impairment	1,154		1,154		1,743
Impaired Financing Receivable, with Related Allowance, Recorded Investment	5,352		5,352		10,319
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	11,043		11,043		721
Financing Receivable, Individually Evaluated for Impairment	16,395		16,395		11,040
Average balance	17,005	11,699	13,815	14,227
Interest income recognized	130	108	379	461
Provision for Loan, Lease, and Other Losses	(799)	4,361	11,294	9,369
Financing Receivable, Allowance for Credit Losses, Write-downs	784	1,414	4,815	2,440
Recoveries	296	227	899	792
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	36,951		36,951		28,984
Financing Receivable, Collectively Evaluated for Impairment	2,195,578		2,195,578		1,977,894
Loans and Leases Receivable, Net Amount	2,211,973		2,211,973		1,988,934
Non-PCI Loans | Commercial | Lease financing
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	1,908		1,908		623
ALLL for loans and leases individually evaluated for impairment	291		291		150
Impaired Financing Receivable, with Related Allowance, Recorded Investment	1,610		1,610		319
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	298		298		304
Financing Receivable, Individually Evaluated for Impairment	1,908		1,908		623
Average balance	1,939	312	1,664	589
Interest income recognized	21	5	55	26
Provision for Loan, Lease, and Other Losses	424	(71)	843	(420)
Financing Receivable, Allowance for Credit Losses, Write-downs	7	28	28	100
Recoveries	16	34	38	71
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	4,848		4,848		4,136
Financing Receivable, Collectively Evaluated for Impairment	690,007		690,007		571,293
Loans and Leases Receivable, Net Amount	691,915		691,915		571,916
Non-PCI Loans | Commercial | Other
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	1,540		1,540		2,000
ALLL for loans and leases individually evaluated for impairment	67		67		1,972
Impaired Financing Receivable, with Related Allowance, Recorded Investment	1,464		1,464		2,000
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0		0		0
Financing Receivable, Individually Evaluated for Impairment	1,464		1,464		2,000
Average balance	1,543	42	1,789	29
Interest income recognized	20	1	20	2
Provision for Loan, Lease, and Other Losses	(58)	127	(2,100)	562
Financing Receivable, Allowance for Credit Losses, Write-downs	0	0	0	13
Recoveries	45	0	91	0
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	1,108		1,108		1,212
Financing Receivable, Collectively Evaluated for Impairment	356,296		356,296		351,833
Loans and Leases Receivable, Net Amount	357,760		357,760		353,833
Non-PCI Loans | Noncommerical | Construction and land development
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	1,045		1,045		1,340
ALLL for loans and leases individually evaluated for impairment	78		78		71
Impaired Financing Receivable, with Related Allowance, Recorded Investment	1,045		1,045		1,077
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0		0		263
Financing Receivable, Individually Evaluated for Impairment	1,045		1,045		1,340
Average balance	1,027	1,942	821	1,902
Interest income recognized	12	27	28	77
Provision for Loan, Lease, and Other Losses	114	21	306	274
Financing Receivable, Allowance for Credit Losses, Write-downs	0	45	22	138
Recoveries	3	14	74	78
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	1,172		1,172		821
Financing Receivable, Collectively Evaluated for Impairment	219,448		219,448		203,676
Loans and Leases Receivable, Net Amount	220,493		220,493		205,016
Non-PCI Loans | Noncommerical | Mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	21,559		21,559		15,746
ALLL for loans and leases individually evaluated for impairment	1,158		1,158		1,360
Impaired Financing Receivable, with Related Allowance, Recorded Investment	9,746		9,746		10,198
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	9,945		9,945		4,715
Financing Receivable, Individually Evaluated for Impairment	19,691		19,691		14,913
Average balance	19,945	15,071	17,376	15,525
Interest income recognized	141	111	401	395
Provision for Loan, Lease, and Other Losses	520	15	2,495	(933)
Financing Receivable, Allowance for Credit Losses, Write-downs	394	231	768	649
Recoveries	314	28	757	184
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	11,987		11,987		9,301
Financing Receivable, Collectively Evaluated for Impairment	2,640,130		2,640,130		2,478,145
Loans and Leases Receivable, Net Amount	2,659,821		2,659,821		2,493,058
Non-PCI Loans | Noncommerical | Revolving mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	6,137		6,137		4,933
ALLL for loans and leases individually evaluated for impairment	526		526		1,052
Impaired Financing Receivable, with Related Allowance, Recorded Investment	2,852		2,852		3,675
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	2,134		2,134		0
Financing Receivable, Individually Evaluated for Impairment	4,986		4,986		3,675
Average balance	5,064	3,708	4,022	4,069
Interest income recognized	29	29	68	105
Provision for Loan, Lease, and Other Losses	871	2,075	440	4,681
Financing Receivable, Allowance for Credit Losses, Write-downs	677	925	2,086	3,249
Recoveries	363	174	843	450
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	17,321		17,321		17,598
Financing Receivable, Collectively Evaluated for Impairment	2,514,986		2,514,986		2,558,125
Loans and Leases Receivable, Net Amount	2,519,972		2,519,972		2,561,800
Non-PCI Loans | Noncommerical | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	1,134		1,134		1,067
ALLL for loans and leases individually evaluated for impairment	498		498		555
Impaired Financing Receivable, with Related Allowance, Recorded Investment	877		877		987
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	221		221		8
Financing Receivable, Individually Evaluated for Impairment	1,098		1,098		995
Average balance	1,176	1,063	1,117	1,710
Interest income recognized	19	19	58	70
Provision for Loan, Lease, and Other Losses	450	1,758	10,029	5,770
Financing Receivable, Allowance for Credit Losses, Write-downs	2,409	2,467	7,935	7,271
Recoveries	762	$ 867	2,270	$ 2,093
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	20,421		20,421		16,000
Financing Receivable, Collectively Evaluated for Impairment	1,190,914		1,190,914		1,116,459
Loans and Leases Receivable, Net Amount	$ 1,192,012		$ 1,192,012		$ 1,117,454