Allowance for Loan and Lease Losses (Allocation of Allowance for Loan and Lease Losses) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	$ 1,665,896	$ 2,092,936
Allowance for loan and lease losses	206,783		$ 206,216
Loans and Leases Receivable, Net Amount	20,210,906		20,033,774
PCI Loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Acquired loans which have adverse change in expected cash flows	479,200		469,300
Provision for Loan, Lease, and Other Losses	(1,997)	(2,864)
Financing Receivable, Allowance for Credit Losses, Write-downs	558	1,146
Recoveries	0	0
PCI Loans | Commercial | Construction and land development
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for Loan, Lease, and Other Losses	(349)	191
Financing Receivable, Allowance for Credit Losses, Write-downs	0	0
Recoveries	0	0
PCI Loans | Commercial | Mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for Loan, Lease, and Other Losses	(980)	(925)
Financing Receivable, Allowance for Credit Losses, Write-downs	108	334
Recoveries	0	0
PCI Loans | Commercial | Other commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for Loan, Lease, and Other Losses	2	119
Financing Receivable, Allowance for Credit Losses, Write-downs	5	0
Recoveries	0	0
PCI Loans | Commercial | Commercial and industrial
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for Loan, Lease, and Other Losses	(220)	(1,031)
Financing Receivable, Allowance for Credit Losses, Write-downs	0	198
Recoveries	0	0
PCI Loans | Noncommercial | Construction and land development
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for Loan, Lease, and Other Losses	0	(152)
Financing Receivable, Allowance for Credit Losses, Write-downs	0	0
Recoveries	0	0
PCI Loans | Noncommercial | Consumer and Other
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for Loan, Lease, and Other Losses	5	452
Financing Receivable, Allowance for Credit Losses, Write-downs	74	456
Recoveries	0	0
PCI Loans | Noncommercial | Mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for Loan, Lease, and Other Losses	(347)	(863)
Financing Receivable, Allowance for Credit Losses, Write-downs	371	85
Recoveries	0	0
PCI Loans | Noncommercial | Revolving mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for Loan, Lease, and Other Losses	(108)	(655)
Financing Receivable, Allowance for Credit Losses, Write-downs	0	73
Recoveries	0	0
Non-PCI Loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Total impaired noncovered loans and leases	140,680		150,367
Unpaid principal balance	156,941		167,966
Impaired Financing Receivable, Related Allowance	6,776		7,200
ALLL for loans and leases individually evaluated for impairment	6,776		7,200
Impaired Financing Receivable, with Related Allowance, Recorded Investment	59,113		66,861
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	81,567		83,506
Financing Receivable, Individually Evaluated for Impairment	140,680		150,367
Average balance	146,442	121,995
Interest income recognized	1,225	1,093
Provision for Loan, Lease, and Other Losses	6,840	8,656
Financing Receivable, Allowance for Credit Losses, Write-downs	6,222	6,030
Recoveries	2,504	2,471
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	186,250		182,704
Financing Receivable, Collectively Evaluated for Impairment	19,331,122		19,139,107
Loans and Leases Receivable, Net Amount	19,471,802		19,289,474
Non-PCI Loans | Commercial | Construction and land development
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	4,602		4,428
ALLL for loans and leases individually evaluated for impairment	83		123
Impaired Financing Receivable, with Related Allowance, Recorded Investment	1,356		1,623
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	1,891		1,471
Financing Receivable, Individually Evaluated for Impairment	3,247		3,094
Average balance	3,164	3,052
Interest income recognized	41	35
Provision for Loan, Lease, and Other Losses	943	1,103
Financing Receivable, Allowance for Credit Losses, Write-downs	426	18
Recoveries	80	62
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	16,802		16,165
Financing Receivable, Collectively Evaluated for Impairment	623,064		617,258
Loans and Leases Receivable, Net Amount	626,311		620,352
Non-PCI Loans | Commercial | Mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	97,320		103,763
ALLL for loans and leases individually evaluated for impairment	3,467		3,370
Impaired Financing Receivable, with Related Allowance, Recorded Investment	37,464		41,793
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	50,984		53,314
Financing Receivable, Individually Evaluated for Impairment	88,448		95,107
Average balance	92,945	80,553
Interest income recognized	766	769
Provision for Loan, Lease, and Other Losses	394	(3,679)
Financing Receivable, Allowance for Credit Losses, Write-downs	90	233
Recoveries	256	761
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	66,989		66,526
Financing Receivable, Collectively Evaluated for Impairment	8,265,183		8,179,441
Loans and Leases Receivable, Net Amount	8,353,631		8,274,548
Non-PCI Loans | Commercial | Other commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	858		863
ALLL for loans and leases individually evaluated for impairment	282		289
Impaired Financing Receivable, with Related Allowance, Recorded Investment	297		305
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	121		122
Financing Receivable, Individually Evaluated for Impairment	418		427
Average balance	423	551
Interest income recognized	5	1
Provision for Loan, Lease, and Other Losses	(104)	458
Financing Receivable, Allowance for Credit Losses, Write-downs	0	169
Recoveries	143	10
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	1,925		1,879
Financing Receivable, Collectively Evaluated for Impairment	324,440		320,594
Loans and Leases Receivable, Net Amount	324,858		321,021
Non-PCI Loans | Commercial | Commercial and industrial
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	16,692		21,455
ALLL for loans and leases individually evaluated for impairment	650		1,118
Impaired Financing Receivable, with Related Allowance, Recorded Investment	5,356		8,544
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	8,364		9,366
Financing Receivable, Individually Evaluated for Impairment	13,720		17,910
Average balance	15,551	14,229
Interest income recognized	151	103
Provision for Loan, Lease, and Other Losses	2,201	7,546
Financing Receivable, Allowance for Credit Losses, Write-downs	1,317	1,713
Recoveries	479	394
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	43,829		41,998
Financing Receivable, Collectively Evaluated for Impairment	2,376,226		2,351,048
Loans and Leases Receivable, Net Amount	2,389,946		2,368,958
Non-PCI Loans | Commercial | Lease financing
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	1,577		1,956
ALLL for loans and leases individually evaluated for impairment	191		213
Impaired Financing Receivable, with Related Allowance, Recorded Investment	1,304		1,651
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	224		104
Financing Receivable, Individually Evaluated for Impairment	1,528		1,755
Average balance	1,657	1,590
Interest income recognized	20	18
Provision for Loan, Lease, and Other Losses	(282)	11
Financing Receivable, Allowance for Credit Losses, Write-downs	0	15
Recoveries	180	11
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	5,231		5,311
Financing Receivable, Collectively Evaluated for Impairment	749,764		729,023
Loans and Leases Receivable, Net Amount	751,292		730,778
Non-PCI Loans | Commercial | Other
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	1,037		1,260
ALLL for loans and leases individually evaluated for impairment	49		0
Impaired Financing Receivable, with Related Allowance, Recorded Investment	898		0
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	62		1,183
Financing Receivable, Individually Evaluated for Impairment	960		1,183
Average balance	1,072	1,990
Interest income recognized	14	0
Provision for Loan, Lease, and Other Losses	(328)	(218)
Financing Receivable, Allowance for Credit Losses, Write-downs	71	0
Recoveries	321	15
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	1,728		1,855
Financing Receivable, Collectively Evaluated for Impairment	342,917		313,649
Loans and Leases Receivable, Net Amount	343,877		314,832
Non-PCI Loans | Noncommercial | Construction and land development
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	416		784
ALLL for loans and leases individually evaluated for impairment	27		49
Impaired Financing Receivable, with Related Allowance, Recorded Investment	416		693
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0		91
Financing Receivable, Individually Evaluated for Impairment	416		784
Average balance	556	658
Interest income recognized	6	7
Provision for Loan, Lease, and Other Losses	87	118
Financing Receivable, Allowance for Credit Losses, Write-downs	0	22
Recoveries	3	68
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	1,548		1,436
Financing Receivable, Collectively Evaluated for Impairment	212,816		219,289
Loans and Leases Receivable, Net Amount	213,232		220,073
Non-PCI Loans | Noncommercial | Mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	24,989		25,043
ALLL for loans and leases individually evaluated for impairment	1,203		1,212
Impaired Financing Receivable, with Related Allowance, Recorded Investment	10,001		10,097
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	14,024		12,889
Financing Receivable, Individually Evaluated for Impairment	24,025		22,986
Average balance	23,500	15,364
Interest income recognized	172	125
Provision for Loan, Lease, and Other Losses	776	813
Financing Receivable, Allowance for Credit Losses, Write-downs	174	284
Recoveries	20	138
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	13,524		12,893
Financing Receivable, Collectively Evaluated for Impairment	2,694,183		2,672,999
Loans and Leases Receivable, Net Amount	2,718,208		2,695,985
Non-PCI Loans | Noncommercial | Revolving mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	8,049		7,120
ALLL for loans and leases individually evaluated for impairment	310		299
Impaired Financing Receivable, with Related Allowance, Recorded Investment	1,059		1,105
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	5,535		4,778
Financing Receivable, Individually Evaluated for Impairment	6,594		5,883
Average balance	6,309	2,986
Interest income recognized	32	16
Provision for Loan, Lease, and Other Losses	1,158	(462)
Financing Receivable, Allowance for Credit Losses, Write-downs	1,036	793
Recoveries	32	134
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	15,815		15,672
Financing Receivable, Collectively Evaluated for Impairment	2,515,308		2,517,223
Loans and Leases Receivable, Net Amount	2,521,902		2,523,106
Non-PCI Loans | Noncommercial | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	1,401		1,294
ALLL for loans and leases individually evaluated for impairment	514		527
Impaired Financing Receivable, with Related Allowance, Recorded Investment	962		1,050
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	362		188
Financing Receivable, Individually Evaluated for Impairment	1,324		1,238
Average balance	1,265	1,022
Interest income recognized	18	19
Provision for Loan, Lease, and Other Losses	1,995	2,966
Financing Receivable, Allowance for Credit Losses, Write-downs	3,108	2,783
Recoveries	990	$ 878
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	18,859		18,969
Financing Receivable, Collectively Evaluated for Impairment	1,227,221		1,218,583
Loans and Leases Receivable, Net Amount	$ 1,228,545		$ 1,219,821