Allowance for Loan and Lease Losses (Allocation of Allowance for Loan and Lease Losses) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	$ 1,199,358	$ 1,614,998	$ 1,199,358	$ 1,614,998
Allowance for loan and lease losses	228,798		228,798		$ 218,795
Loans and Leases Receivable, Net Amount	22,642,667		22,642,667		21,519,083
PCI Loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Acquired loans which have adverse change in expected cash flows	351,600		351,600		359,700
Provision for Loan, Lease, and Other Losses	2,572	(2,146)	(273)	(4,143)
Financing Receivable, Allowance for Credit Losses, Write-downs	0	56	0	614
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	280	(453)	94	(802)
Financing Receivable, Allowance for Credit Losses, Write-downs	0	0	0	0
Recoveries	0	0	0	0
PCI Loans | Commercial | Mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for Loan, Lease, and Other Losses	1,604	(935)	374	(1,914)
Financing Receivable, Allowance for Credit Losses, Write-downs	0	56	0	165
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	10	(154)	(148)	(152)
Financing Receivable, Allowance for Credit Losses, Write-downs	0	0	0	5
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	94	60	(48)	(160)
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	23	(105)	(11)	(101)
Financing Receivable, Allowance for Credit Losses, Write-downs	0	0	0	73
Recoveries	0	0	0	0
PCI Loans | Noncommercial | Mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for Loan, Lease, and Other Losses	556	(382)	11	(729)
Financing Receivable, Allowance for Credit Losses, Write-downs	0	0	0	371
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	5	(177)	(545)	(285)
Financing Receivable, Allowance for Credit Losses, Write-downs	0	0	0	0
Recoveries	0	0	0	0
Non-PCI Loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Total impaired noncovered loans and leases	143,381		143,381		136,399
Unpaid principal balance	155,812		155,812		150,189
Impaired Financing Receivable, Related Allowance	9,664		9,664		9,210
ALLL for loans and leases individually evaluated for impairment	9,664		9,664		9,210
Impaired Financing Receivable, with Related Allowance, Recorded Investment	82,737		82,737		79,491
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	60,644		60,644		56,908
Financing Receivable, Individually Evaluated for Impairment	143,381		143,381		136,399
Average balance	139,608	128,759	138,144	137,601
Interest income recognized	1,179	1,015	2,327	2,240
Provision for Loan, Lease, and Other Losses	9,752	6,708	20,828	13,548
Financing Receivable, Allowance for Credit Losses, Write-downs	9,423	5,841	18,194	12,061
Recoveries	4,954	2,560	7,642	5,062
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	205,638		205,638		195,816
Financing Receivable, Collectively Evaluated for Impairment	21,833,221		21,833,221		20,792,310
Loans and Leases Receivable, Net Amount	21,976,602		21,976,602		20,928,709
Non-PCI Loans | Commercial | Construction and land development
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	932		932		1,172
ALLL for loans and leases individually evaluated for impairment	93		93		151
Impaired Financing Receivable, with Related Allowance, Recorded Investment	554		554		1,002
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	274		274		43
Financing Receivable, Individually Evaluated for Impairment	828		828		1,045
Average balance	970	3,236	1,013	3,200
Interest income recognized	11	40	23	81
Provision for Loan, Lease, and Other Losses	2,372	291	4,908	1,234
Financing Receivable, Allowance for Credit Losses, Write-downs	413	136	490	562
Recoveries	209	129	264	209
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	33,466		33,466		28,726
Financing Receivable, Collectively Evaluated for Impairment	739,463		739,463		648,112
Loans and Leases Receivable, Net Amount	740,291		740,291		649,157
Non-PCI Loans | Commercial | Mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	80,633		80,633		82,658
ALLL for loans and leases individually evaluated for impairment	4,166		4,166		3,488
Impaired Financing Receivable, with Related Allowance, Recorded Investment	41,376		41,376		42,875
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	33,292		33,292		33,486
Financing Receivable, Individually Evaluated for Impairment	74,668		74,668		76,361
Average balance	74,121	79,442	74,715	86,193
Interest income recognized	651	616	1,293	1,382
Provision for Loan, Lease, and Other Losses	639	701	645	1,096
Financing Receivable, Allowance for Credit Losses, Write-downs	235	44	272	134
Recoveries	731	500	1,095	755
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	45,580		45,580		44,790
Financing Receivable, Collectively Evaluated for Impairment	9,226,486		9,226,486		8,949,859
Loans and Leases Receivable, Net Amount	9,301,154		9,301,154		9,026,220
Non-PCI Loans | Commercial | Other commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	1,877		1,877		1,880
ALLL for loans and leases individually evaluated for impairment	225		225		152
Impaired Financing Receivable, with Related Allowance, Recorded Investment	1,133		1,133		1,279
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	434		434		284
Financing Receivable, Individually Evaluated for Impairment	1,567		1,567		1,563
Average balance	1,525	878	1,555	651
Interest income recognized	9	7	17	12
Provision for Loan, Lease, and Other Losses	33	(79)	337	(184)
Financing Receivable, Allowance for Credit Losses, Write-downs	0	0	5	0
Recoveries	7	10	11	154
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	3,387		3,387		3,117
Financing Receivable, Collectively Evaluated for Impairment	361,772		361,772		349,728
Loans and Leases Receivable, Net Amount	363,339		363,339		351,291
Non-PCI Loans | Commercial | Commercial and industrial
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	11,983		11,983		16,637
ALLL for loans and leases individually evaluated for impairment	623		623		1,732
Impaired Financing Receivable, with Related Allowance, Recorded Investment	6,135		6,135		8,920
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	3,621		3,621		3,680
Financing Receivable, Individually Evaluated for Impairment	9,756		9,756		12,600
Average balance	10,159	9,938	10,844	12,744
Interest income recognized	98	84	202	235
Provision for Loan, Lease, and Other Losses	968	81	4,560	2,282
Financing Receivable, Allowance for Credit Losses, Write-downs	3,121	1,177	6,374	2,494
Recoveries	2,392	525	2,657	1,004
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	50,445		50,445		48,493
Financing Receivable, Collectively Evaluated for Impairment	2,543,856		2,543,856		2,554,901
Loans and Leases Receivable, Net Amount	2,553,612		2,553,612		2,567,501
Non-PCI Loans | Commercial | Lease financing
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	1,785		1,785		1,074
ALLL for loans and leases individually evaluated for impairment	66		66		75
Impaired Financing Receivable, with Related Allowance, Recorded Investment	1,591		1,591		1,002
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	194		194		72
Financing Receivable, Individually Evaluated for Impairment	1,785		1,785		1,074
Average balance	1,911	1,214	1,740	1,436
Interest income recognized	14	15	28	35
Provision for Loan, Lease, and Other Losses	186	343	761	62
Financing Receivable, Allowance for Credit Losses, Write-downs	97	0	270	0
Recoveries	0	1	6	180
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	6,338		6,338		5,832
Financing Receivable, Collectively Evaluated for Impairment	852,158		852,158		825,196
Loans and Leases Receivable, Net Amount	853,943		853,943		826,270
Non-PCI Loans | Commercial | Other
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	662		662		233
ALLL for loans and leases individually evaluated for impairment	0		0		23
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0		0		142
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	662		662		0
Financing Receivable, Individually Evaluated for Impairment	662		662		142
Average balance	434	813	315	943
Interest income recognized	5	10	7	24
Provision for Loan, Lease, and Other Losses	(214)	37	241	(290)
Financing Receivable, Allowance for Credit Losses, Write-downs	64	88	187	160
Recoveries	46	29	121	350
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	3,302		3,302		3,104
Financing Receivable, Collectively Evaluated for Impairment	485,911		485,911		340,122
Loans and Leases Receivable, Net Amount	486,573		486,573		340,264
Non-PCI Loans | Noncommercial | Construction and land development
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	4,393		4,393		3,030
ALLL for loans and leases individually evaluated for impairment	86		86		109
Impaired Financing Receivable, with Related Allowance, Recorded Investment	795		795		645
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	2,906		2,906		1,968
Financing Receivable, Individually Evaluated for Impairment	3,701		3,701		2,613
Average balance	3,185	413	2,895	485
Interest income recognized	33	5	66	11
Provision for Loan, Lease, and Other Losses	(10)	78	(93)	165
Financing Receivable, Allowance for Credit Losses, Write-downs	0	0	0	0
Recoveries	0	0	0	3
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	1,417		1,417		1,487
Financing Receivable, Collectively Evaluated for Impairment	214,532		214,532		228,787
Loans and Leases Receivable, Net Amount	218,233		218,233		231,400
Non-PCI Loans | Noncommercial | Mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	40,972		40,972		32,588
ALLL for loans and leases individually evaluated for impairment	2,687		2,687		2,447
Impaired Financing Receivable, with Related Allowance, Recorded Investment	23,899		23,899		20,269
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	15,438		15,438		11,207
Financing Receivable, Individually Evaluated for Impairment	39,337		39,337		31,476
Average balance	36,767	24,982	34,864	24,240
Interest income recognized	272	178	525	350
Provision for Loan, Lease, and Other Losses	155	1,487	1,506	2,262
Financing Receivable, Allowance for Credit Losses, Write-downs	222	179	472	352
Recoveries	75	41	362	61
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	13,156		13,156		12,000
Financing Receivable, Collectively Evaluated for Impairment	3,266,024		3,266,024		2,857,648
Loans and Leases Receivable, Net Amount	3,305,361		3,305,361		2,889,124
Non-PCI Loans | Noncommercial | Revolving mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	10,054		10,054		8,831
ALLL for loans and leases individually evaluated for impairment	1,086		1,086		366
Impaired Financing Receivable, with Related Allowance, Recorded Investment	5,708		5,708		1,825
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	3,096		3,096		5,788
Financing Receivable, Individually Evaluated for Impairment	8,804		8,804		7,613
Average balance	8,484	6,421	8,227	6,365
Interest income recognized	62	40	119	72
Provision for Loan, Lease, and Other Losses	1,054	1,470	1,604	2,628
Financing Receivable, Allowance for Credit Losses, Write-downs	280	1,081	1,105	2,116
Recoveries	401	214	953	245
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	21,379		21,379		20,647
Financing Receivable, Collectively Evaluated for Impairment	2,669,882		2,669,882		2,593,731
Loans and Leases Receivable, Net Amount	2,678,686		2,678,686		2,601,344
Non-PCI Loans | Noncommercial | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	2,521		2,521		2,086
ALLL for loans and leases individually evaluated for impairment	632		632		667
Impaired Financing Receivable, with Related Allowance, Recorded Investment	1,546		1,546		1,532
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	727		727		380
Financing Receivable, Individually Evaluated for Impairment	2,273		2,273		1,912
Average balance	2,052	1,422	1,976	1,344
Interest income recognized	24	20	47	38
Provision for Loan, Lease, and Other Losses	4,569	2,299	6,359	4,293
Financing Receivable, Allowance for Credit Losses, Write-downs	4,991	3,136	9,019	6,243
Recoveries	1,093	$ 1,111	2,173	$ 2,101
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	27,168		27,168		27,620
Financing Receivable, Collectively Evaluated for Impairment	1,473,137		1,473,137		1,444,226
Loans and Leases Receivable, Net Amount	$ 1,475,410		$ 1,475,410		$ 1,446,138