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, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	$ 1,475,149	$ 1,788,136	$ 1,475,149	$ 1,788,136
Allowance for loan and lease losses	211,950		211,950		$ 206,216
Loans and Leases Receivable, Net Amount	21,085,030		21,085,030		20,033,774
PCI Loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Acquired loans which have adverse change in expected cash flows	325,900		325,900		469,300
Provision for Loan, Lease, and Other Losses	77	2,769	(4,066)	(1,370)
Financing Receivable, Allowance for Credit Losses, Write-downs	0	680	614	2,702
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	74	632	(728)	1,148
Financing Receivable, Allowance for Credit Losses, Write-downs	0	0	0	97
Recoveries	0	0	0	0
PCI Loans | Commercial | Mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for Loan, Lease, and Other Losses	406	2,187	(1,508)	(803)
Financing Receivable, Allowance for Credit Losses, Write-downs	0	48	165	765
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	(378)	235	(530)	229
Financing Receivable, Allowance for Credit Losses, Write-downs	0	0	5	0
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	101	118	(59)	(514)
Financing Receivable, Allowance for Credit Losses, Write-downs	0	39	0	324
Recoveries	0	0	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	0	0	(183)
Financing Receivable, Allowance for Credit Losses, Write-downs	0	0	0	0
Recoveries	0	0	0	0
PCI Loans | Noncommercial | Consumer and Other
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for Loan, Lease, and Other Losses	29	29	(72)	650
Financing Receivable, Allowance for Credit Losses, Write-downs	0	1	73	463
Recoveries	0	0	0	0
PCI Loans | Noncommercial | Mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for Loan, Lease, and Other Losses	(134)	(281)	(863)	21
Financing Receivable, Allowance for Credit Losses, Write-downs	0	15	371	295
Recoveries	0	0	0	0
PCI Loans | Noncommercial | Revolving mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for Loan, Lease, and Other Losses	(21)	(151)	(306)	(1,918)
Financing Receivable, Allowance for Credit Losses, Write-downs	0	577	0	758
Recoveries	0	0	0	0
Non-PCI Loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Total impaired noncovered loans and leases	136,000		136,000		150,367
Unpaid principal balance	146,573		146,573		167,966
Impaired Financing Receivable, Related Allowance	8,372		8,372		7,200
ALLL for loans and leases individually evaluated for impairment	8,372		8,372		7,200
Impaired Financing Receivable, with Related Allowance, Recorded Investment	69,751		69,751		66,861
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	66,249		66,249		83,506
Financing Receivable, Individually Evaluated for Impairment	136,000		136,000		150,367
Average balance	132,572	151,108	135,925	132,864
Interest income recognized	1,090	1,218	3,330	3,528
Provision for Loan, Lease, and Other Losses	7,430	(2,662)	20,978	14,988
Financing Receivable, Allowance for Credit Losses, Write-downs	6,210	5,018	17,953	17,098
Recoveries	2,645	2,737	7,389	7,179
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	191,946		191,946		182,704
Financing Receivable, Collectively Evaluated for Impairment	20,292,780		20,292,780		19,139,107
Loans and Leases Receivable, Net Amount	20,428,780		20,428,780		19,289,474
Non-PCI Loans | Commercial | Construction and land development
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	3,819		3,819		4,428
ALLL for loans and leases individually evaluated for impairment	239		239		123
Impaired Financing Receivable, with Related Allowance, Recorded Investment	1,824		1,824		1,623
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	1,480		1,480		1,471
Financing Receivable, Individually Evaluated for Impairment	3,304		3,304		3,094
Average balance	3,297	3,257	3,232	3,148
Interest income recognized	44	37	125	107
Provision for Loan, Lease, and Other Losses	835	1,189	2,069	2,380
Financing Receivable, Allowance for Credit Losses, Write-downs	77	336	639	575
Recoveries	69	129	278	295
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	17,757		17,757		16,165
Financing Receivable, Collectively Evaluated for Impairment	638,854		638,854		617,258
Loans and Leases Receivable, Net Amount	642,158		642,158		620,352
Non-PCI Loans | Commercial | Mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	86,354		86,354		103,763
ALLL for loans and leases individually evaluated for impairment	3,126		3,126		3,370
Impaired Financing Receivable, with Related Allowance, Recorded Investment	35,987		35,987		41,793
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	43,846		43,846		53,314
Financing Receivable, Individually Evaluated for Impairment	79,833		79,833		95,107
Average balance	78,994	99,613	83,794	88,614
Interest income recognized	642	803	2,024	2,405
Provision for Loan, Lease, and Other Losses	(2,163)	(5,664)	(1,067)	(11,221)
Financing Receivable, Allowance for Credit Losses, Write-downs	461	411	454	691
Recoveries	378	794	992	1,878
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	66,241		66,241		66,526
Financing Receivable, Collectively Evaluated for Impairment	8,699,299		8,699,299		8,179,441
Loans and Leases Receivable, Net Amount	8,779,132		8,779,132		8,274,548
Non-PCI Loans | Commercial | Other commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	1,923		1,923		863
ALLL for loans and leases individually evaluated for impairment	118		118		289
Impaired Financing Receivable, with Related Allowance, Recorded Investment	585		585		305
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	1,016		1,016		122
Financing Receivable, Individually Evaluated for Impairment	1,601		1,601		427
Average balance	1,571	539	957	498
Interest income recognized	13	6	25	7
Provision for Loan, Lease, and Other Losses	150	291	(34)	522
Financing Receivable, Allowance for Credit Losses, Write-downs	0	0	0	178
Recoveries	13	15	167	34
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	2,183		2,183		1,879
Financing Receivable, Collectively Evaluated for Impairment	344,429		344,429		320,594
Loans and Leases Receivable, Net Amount	346,030		346,030		321,021
Non-PCI Loans | Commercial | Commercial and industrial
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	11,133		11,133		21,455
ALLL for loans and leases individually evaluated for impairment	1,059		1,059		1,118
Impaired Financing Receivable, with Related Allowance, Recorded Investment	6,518		6,518		8,544
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	4,154		4,154		9,366
Financing Receivable, Individually Evaluated for Impairment	10,672		10,672		17,910
Average balance	9,676	17,005	11,722	13,815
Interest income recognized	84	130	319	379
Provision for Loan, Lease, and Other Losses	2,954	(799)	5,236	11,294
Financing Receivable, Allowance for Credit Losses, Write-downs	1,198	784	3,690	4,815
Recoveries	328	296	1,330	899
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	44,933		44,933		41,998
Financing Receivable, Collectively Evaluated for Impairment	2,496,495		2,496,495		2,351,048
Loans and Leases Receivable, Net Amount	2,507,167		2,507,167		2,368,958
Non-PCI Loans | Commercial | Lease financing
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	1,153		1,153		1,956
ALLL for loans and leases individually evaluated for impairment	45		45		213
Impaired Financing Receivable, with Related Allowance, Recorded Investment	1,003		1,003		1,651
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	143		143		104
Financing Receivable, Individually Evaluated for Impairment	1,146		1,146		1,755
Average balance	1,169	1,939	1,347	1,664
Interest income recognized	14	21	49	55
Provision for Loan, Lease, and Other Losses	274	424	337	843
Financing Receivable, Allowance for Credit Losses, Write-downs	132	7	93	28
Recoveries	5	16	145	38
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	5,868		5,868		5,311
Financing Receivable, Collectively Evaluated for Impairment	802,455		802,455		729,023
Loans and Leases Receivable, Net Amount	803,601		803,601		730,778
Non-PCI Loans | Commercial | Other
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	532		532		1,260
ALLL for loans and leases individually evaluated for impairment	22		22		0
Impaired Financing Receivable, with Related Allowance, Recorded Investment	125		125		0
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	318		318		1,183
Financing Receivable, Individually Evaluated for Impairment	443		443		1,183
Average balance	569	1,543	818	1,789
Interest income recognized	6	20	30	20
Provision for Loan, Lease, and Other Losses	183	(58)	(109)	(2,100)
Financing Receivable, Allowance for Credit Losses, Write-downs	0	0	22	0
Recoveries	170	45	384	91
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	2,086		2,086		1,855
Financing Receivable, Collectively Evaluated for Impairment	325,905		325,905		313,649
Loans and Leases Receivable, Net Amount	326,348		326,348		314,832
Non-PCI Loans | Noncommercial | Construction and land development
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	406		406		784
ALLL for loans and leases individually evaluated for impairment	0		0		49
Impaired Financing Receivable, with Related Allowance, Recorded Investment	163		163		693
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	243		243		91
Financing Receivable, Individually Evaluated for Impairment	406		406		784
Average balance	408	1,027	459	821
Interest income recognized	5	12	16	28
Provision for Loan, Lease, and Other Losses	88	114	253	306
Financing Receivable, Allowance for Credit Losses, Write-downs	0	0	0	22
Recoveries	0	3	3	74
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	1,741		1,741		1,436
Financing Receivable, Collectively Evaluated for Impairment	233,977		233,977		219,289
Loans and Leases Receivable, Net Amount	234,383		234,383		220,073
Non-PCI Loans | Noncommercial | Mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	30,353		30,353		25,043
ALLL for loans and leases individually evaluated for impairment	2,077		2,077		1,212
Impaired Financing Receivable, with Related Allowance, Recorded Investment	16,897		16,897		10,097
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	12,430		12,430		12,889
Financing Receivable, Individually Evaluated for Impairment	29,327		29,327		22,986
Average balance	28,008	19,945	25,497	17,376
Interest income recognized	214	141	564	401
Provision for Loan, Lease, and Other Losses	531	520	2,794	2,495
Financing Receivable, Allowance for Credit Losses, Write-downs	328	394	680	768
Recoveries	334	314	394	757
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	14,536		14,536		12,893
Financing Receivable, Collectively Evaluated for Impairment	2,784,587		2,784,587		2,672,999
Loans and Leases Receivable, Net Amount	2,813,914		2,813,914		2,695,985
Non-PCI Loans | Noncommercial | Revolving mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	9,245		9,245		7,120
ALLL for loans and leases individually evaluated for impairment	1,046		1,046		299
Impaired Financing Receivable, with Related Allowance, Recorded Investment	5,266		5,266		1,105
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	2,442		2,442		4,778
Financing Receivable, Individually Evaluated for Impairment	7,708		7,708		5,883
Average balance	7,373	5,064	6,701	4,022
Interest income recognized	48	29	120	68
Provision for Loan, Lease, and Other Losses	679	871	3,306	440
Financing Receivable, Allowance for Credit Losses, Write-downs	391	677	2,507	2,086
Recoveries	256	363	502	843
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	16,226		16,226		15,672
Financing Receivable, Collectively Evaluated for Impairment	2,565,378		2,565,378		2,517,223
Loans and Leases Receivable, Net Amount	2,573,086		2,573,086		2,523,106
Non-PCI Loans | Noncommercial | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	1,655		1,655		1,294
ALLL for loans and leases individually evaluated for impairment	640		640		527
Impaired Financing Receivable, with Related Allowance, Recorded Investment	1,383		1,383		1,050
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	177		177		188
Financing Receivable, Individually Evaluated for Impairment	1,560		1,560		1,238
Average balance	1,507	1,176	1,398	1,117
Interest income recognized	20	19	58	58
Provision for Loan, Lease, and Other Losses	3,899	450	8,193	10,029
Financing Receivable, Allowance for Credit Losses, Write-downs	3,623	2,409	9,868	7,935
Recoveries	1,092	$ 762	3,194	$ 2,270
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	20,375		20,375		18,969
Financing Receivable, Collectively Evaluated for Impairment	1,401,401		1,401,401		1,218,583
Loans and Leases Receivable, Net Amount	$ 1,402,961		$ 1,402,961		$ 1,219,821