Allowance for Loan and Lease Losses (Allocation of Allowance for Loan and Lease Losses) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	$ 1,155,034	$ 1,665,896
Allowance for loan and lease losses	220,943		$ 218,795
Loans and Leases Receivable, Net Amount	21,685,506		21,519,083
PCI Loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Acquired loans which have adverse change in expected cash flows	275,800		359,700
Provision for Loan, Lease, and Other Losses	(2,845)	(1,997)
Financing Receivable, Allowance for Credit Losses, Write-downs	0	558
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	(186)	(349)
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	(1,230)	(980)
Financing Receivable, Allowance for Credit Losses, Write-downs	0	108
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	(158)	2
Financing Receivable, Allowance for Credit Losses, Write-downs	0	5
Recoveries	0	0
PCI Loans | Commercial | Commercial and industrial
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for Loan, Lease, and Other Losses	(142)	(220)
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	(34)	5
Financing Receivable, Allowance for Credit Losses, Write-downs	0	74
Recoveries	0	0
PCI Loans | Noncommercial | Mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for Loan, Lease, and Other Losses	(545)	(347)
Financing Receivable, Allowance for Credit Losses, Write-downs	0	371
Recoveries	0	0
PCI Loans | Noncommercial | Revolving mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for Loan, Lease, and Other Losses	(550)	(108)
Financing Receivable, Allowance for Credit Losses, Write-downs	0	0
Recoveries	0	0
Non-PCI Loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Total impaired noncovered loans and leases	137,711		136,399
Unpaid principal balance	150,303		150,189
Impaired Financing Receivable, Related Allowance	8,852		9,210
ALLL for loans and leases individually evaluated for impairment	8,852		9,210
Impaired Financing Receivable, with Related Allowance, Recorded Investment	76,029		79,491
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	61,682		56,908
Financing Receivable, Individually Evaluated for Impairment	137,711		136,399
Average balance	136,679	146,442
Interest income recognized	1,148	1,225
Provision for Loan, Lease, and Other Losses	11,076	6,840
Financing Receivable, Allowance for Credit Losses, Write-downs	8,709	6,222
Recoveries	2,626	2,504
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	201,167		195,816
Financing Receivable, Collectively Evaluated for Impairment	20,919,922		20,792,310
Loans and Leases Receivable, Net Amount	21,057,633		20,928,709
Non-PCI Loans | Commercial | Construction and land development
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	1,191		1,172
ALLL for loans and leases individually evaluated for impairment	151		151
Impaired Financing Receivable, with Related Allowance, Recorded Investment	750		1,002
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	308		43
Financing Receivable, Individually Evaluated for Impairment	1,058		1,045
Average balance	1,055	3,164
Interest income recognized	12	41
Provision for Loan, Lease, and Other Losses	2,536	943
Financing Receivable, Allowance for Credit Losses, Write-downs	77	426
Recoveries	55	80
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	31,240		28,726
Financing Receivable, Collectively Evaluated for Impairment	682,357		648,112
Loans and Leases Receivable, Net Amount	683,415		649,157
Non-PCI Loans | Commercial | Mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	81,232		82,658
ALLL for loans and leases individually evaluated for impairment	3,122		3,488
Impaired Financing Receivable, with Related Allowance, Recorded Investment	38,730		42,875
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	36,058		33,486
Financing Receivable, Individually Evaluated for Impairment	74,788		76,361
Average balance	75,310	92,945
Interest income recognized	642	766
Provision for Loan, Lease, and Other Losses	6	394
Financing Receivable, Allowance for Credit Losses, Write-downs	37	90
Recoveries	364	256
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	45,489		44,790
Financing Receivable, Collectively Evaluated for Impairment	9,098,824		8,949,859
Loans and Leases Receivable, Net Amount	9,173,612		9,026,220
Non-PCI Loans | Commercial | Other commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	1,810		1,880
ALLL for loans and leases individually evaluated for impairment	132		152
Impaired Financing Receivable, with Related Allowance, Recorded Investment	1,052		1,279
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	445		284
Financing Receivable, Individually Evaluated for Impairment	1,497		1,563
Average balance	1,584	423
Interest income recognized	8	5
Provision for Loan, Lease, and Other Losses	304	(104)
Financing Receivable, Allowance for Credit Losses, Write-downs	5	0
Recoveries	4	143
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	3,440		3,117
Financing Receivable, Collectively Evaluated for Impairment	363,365		349,728
Loans and Leases Receivable, Net Amount	364,862		351,291
Non-PCI Loans | Commercial | Commercial and industrial
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	13,244		16,637
ALLL for loans and leases individually evaluated for impairment	1,043		1,732
Impaired Financing Receivable, with Related Allowance, Recorded Investment	8,053		8,920
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	2,811		3,680
Financing Receivable, Individually Evaluated for Impairment	10,864		12,600
Average balance	11,529	15,551
Interest income recognized	104	151
Provision for Loan, Lease, and Other Losses	3,592	2,201
Financing Receivable, Allowance for Credit Losses, Write-downs	3,253	1,317
Recoveries	265	479
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	49,786		48,493
Financing Receivable, Collectively Evaluated for Impairment	2,467,047		2,554,901
Loans and Leases Receivable, Net Amount	2,477,911		2,567,501
Non-PCI Loans | Commercial | Lease financing
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	2,054		1,074
ALLL for loans and leases individually evaluated for impairment	213		75
Impaired Financing Receivable, with Related Allowance, Recorded Investment	1,808		1,002
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	246		72
Financing Receivable, Individually Evaluated for Impairment	2,054		1,074
Average balance	1,568	1,657
Interest income recognized	14	20
Provision for Loan, Lease, and Other Losses	575	(282)
Financing Receivable, Allowance for Credit Losses, Write-downs	173	0
Recoveries	6	180
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	6,102		5,832
Financing Receivable, Collectively Evaluated for Impairment	838,147		825,196
Loans and Leases Receivable, Net Amount	840,201		826,270
Non-PCI Loans | Commercial | Other
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	274		233
ALLL for loans and leases individually evaluated for impairment	21		23
Impaired Financing Receivable, with Related Allowance, Recorded Investment	116		142
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	143		0
Financing Receivable, Individually Evaluated for Impairment	259		142
Average balance	196	1,072
Interest income recognized	2	14
Provision for Loan, Lease, and Other Losses	517	(328)
Financing Receivable, Allowance for Credit Losses, Write-downs	123	71
Recoveries	13	321
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	3,513		3,104
Financing Receivable, Collectively Evaluated for Impairment	321,093		340,122
Loans and Leases Receivable, Net Amount	321,352		340,264
Non-PCI Loans | Noncommercial | Construction and land development
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	3,044		3,030
ALLL for loans and leases individually evaluated for impairment	103		109
Impaired Financing Receivable, with Related Allowance, Recorded Investment	862		645
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	1,715		1,968
Financing Receivable, Individually Evaluated for Impairment	2,577		2,613
Average balance	2,605	556
Interest income recognized	33	6
Provision for Loan, Lease, and Other Losses	(83)	87
Financing Receivable, Allowance for Credit Losses, Write-downs	0	0
Recoveries	0	3
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	1,410		1,487
Financing Receivable, Collectively Evaluated for Impairment	215,526		228,787
Loans and Leases Receivable, Net Amount	218,103		231,400
Non-PCI Loans | Noncommercial | Mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	35,863		32,588
ALLL for loans and leases individually evaluated for impairment	3,189		2,447
Impaired Financing Receivable, with Related Allowance, Recorded Investment	21,606		20,269
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	12,878		11,207
Financing Receivable, Individually Evaluated for Impairment	34,484		31,476
Average balance	32,963	23,500
Interest income recognized	253	172
Provision for Loan, Lease, and Other Losses	1,061	776
Financing Receivable, Allowance for Credit Losses, Write-downs	250	174
Recoveries	287	20
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	21,003		20,647
Financing Receivable, Collectively Evaluated for Impairment	2,910,877		2,857,648
Loans and Leases Receivable, Net Amount	2,945,361		2,889,124
Non-PCI Loans | Noncommercial | Revolving mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	9,535		8,831
ALLL for loans and leases individually evaluated for impairment	287		366
Impaired Financing Receivable, with Related Allowance, Recorded Investment	1,627		1,825
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	6,645		5,788
Financing Receivable, Individually Evaluated for Impairment	8,272		7,613
Average balance	7,969	6,309
Interest income recognized	57	32
Provision for Loan, Lease, and Other Losses	840	1,158
Financing Receivable, Allowance for Credit Losses, Write-downs	825	1,036
Recoveries	552	32
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	12,646		12,000
Financing Receivable, Collectively Evaluated for Impairment	2,595,884		2,593,731
Loans and Leases Receivable, Net Amount	2,604,156		2,601,344
Non-PCI Loans | Noncommercial | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	2,056		2,086
ALLL for loans and leases individually evaluated for impairment	591		667
Impaired Financing Receivable, with Related Allowance, Recorded Investment	1,425		1,532
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	433		380
Financing Receivable, Individually Evaluated for Impairment	1,858		1,912
Average balance	1,900	1,265
Interest income recognized	23	18
Provision for Loan, Lease, and Other Losses	1,728	1,995
Financing Receivable, Allowance for Credit Losses, Write-downs	3,966	3,108
Recoveries	1,080	$ 990
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	26,538		27,620
Financing Receivable, Collectively Evaluated for Impairment	1,426,802		1,444,226
Loans and Leases Receivable, Net Amount	$ 1,428,660		$ 1,446,138