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, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	$ 1,293,760	$ 1,475,149	$ 1,293,760	$ 1,475,149
Allowance for loan and lease losses	231,842		231,842		$ 218,795
Loans and Leases Receivable, Net Amount	22,917,231		22,917,231		21,519,083
PCI Loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Acquired loans which have adverse change in expected cash flows	310,000		310,000		359,700
Provision for Loan, Lease, and Other Losses	(537)	77	(810)	(4,066)
Financing Receivable, Allowance for Credit Losses, Write-downs	0	0	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	(78)	74	16	(728)
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	(15)	406	359	(1,508)
Financing Receivable, Allowance for Credit Losses, Write-downs	0	0	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	(146)	(378)	(294)	(530)
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	(133)	101	(181)	(59)
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	53	29	42	(72)
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	(184)	(134)	(173)	(863)
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	(34)	(21)	(579)	(306)
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	143,042		143,042		136,399
Unpaid principal balance	154,149		154,149		150,189
Impaired Financing Receivable, Related Allowance	10,132		10,132		9,210
ALLL for loans and leases individually evaluated for impairment	10,132		10,132		9,210
Impaired Financing Receivable, with Related Allowance, Recorded Investment	79,378		79,378		79,491
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	63,664		63,664		56,908
Financing Receivable, Individually Evaluated for Impairment	143,042		143,042		136,399
Average balance	142,648	132,572	139,645	135,925
Interest income recognized	1,225	1,090	3,552	3,330
Provision for Loan, Lease, and Other Losses	8,483	7,430	29,311	20,978
Financing Receivable, Allowance for Credit Losses, Write-downs	8,494	6,210	26,688	17,953
Recoveries	3,592	2,645	11,234	7,389
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	208,751		208,751		195,816
Financing Receivable, Collectively Evaluated for Impairment	22,171,864		22,171,864		20,792,310
Loans and Leases Receivable, Net Amount	22,314,906		22,314,906		20,928,709
Non-PCI Loans | Commercial | Construction and land development
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	648		648		1,172
ALLL for loans and leases individually evaluated for impairment	91		91		151
Impaired Financing Receivable, with Related Allowance, Recorded Investment	526		526		1,002
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	17		17		43
Financing Receivable, Individually Evaluated for Impairment	543		543		1,045
Average balance	754	3,297	926	3,232
Interest income recognized	8	44	31	125
Provision for Loan, Lease, and Other Losses	(5,150)	835	(242)	2,069
Financing Receivable, Allowance for Credit Losses, Write-downs	9	77	499	639
Recoveries	56	69	320	278
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	28,365		28,365		28,726
Financing Receivable, Collectively Evaluated for Impairment	626,344		626,344		648,112
Loans and Leases Receivable, Net Amount	626,887		626,887		649,157
Non-PCI Loans | Commercial | Mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	76,859		76,859		82,658
ALLL for loans and leases individually evaluated for impairment	3,916		3,916		3,488
Impaired Financing Receivable, with Related Allowance, Recorded Investment	38,286		38,286		42,875
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	33,666		33,666		33,486
Financing Receivable, Individually Evaluated for Impairment	71,952		71,952		76,361
Average balance	73,099	78,994	74,177	83,794
Interest income recognized	653	642	1,946	2,024
Provision for Loan, Lease, and Other Losses	(71)	(2,163)	574	(1,067)
Financing Receivable, Allowance for Credit Losses, Write-downs	39	461	311	454
Recoveries	1,446	378	2,541	992
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	47,166		47,166		44,790
Financing Receivable, Collectively Evaluated for Impairment	9,438,206		9,438,206		8,949,859
Loans and Leases Receivable, Net Amount	9,510,158		9,510,158		9,026,220
Non-PCI Loans | Commercial | Other commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	1,939		1,939		1,880
ALLL for loans and leases individually evaluated for impairment	204		204		152
Impaired Financing Receivable, with Related Allowance, Recorded Investment	1,254		1,254		1,279
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	362		362		284
Financing Receivable, Individually Evaluated for Impairment	1,616		1,616		1,563
Average balance	1,720	1,571	1,610	957
Interest income recognized	8	13	25	25
Provision for Loan, Lease, and Other Losses	891	150	1,228	(34)
Financing Receivable, Allowance for Credit Losses, Write-downs	0	0	5	0
Recoveries	8	13	19	167
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	4,307		4,307		3,117
Financing Receivable, Collectively Evaluated for Impairment	433,120		433,120		349,728
Loans and Leases Receivable, Net Amount	434,736		434,736		351,291
Non-PCI Loans | Commercial | Commercial and industrial
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	11,568		11,568		16,637
ALLL for loans and leases individually evaluated for impairment	1,260		1,260		1,732
Impaired Financing Receivable, with Related Allowance, Recorded Investment	7,433		7,433		8,920
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	2,445		2,445		3,680
Financing Receivable, Individually Evaluated for Impairment	9,878		9,878		12,600
Average balance	9,501	9,676	10,396	11,722
Interest income recognized	96	84	298	319
Provision for Loan, Lease, and Other Losses	5,621	2,954	10,181	5,236
Financing Receivable, Allowance for Credit Losses, Write-downs	1,275	1,198	7,649	3,690
Recoveries	433	328	3,090	1,330
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	54,587		54,587		48,493
Financing Receivable, Collectively Evaluated for Impairment	2,645,020		2,645,020		2,554,901
Loans and Leases Receivable, Net Amount	2,654,898		2,654,898		2,567,501
Non-PCI Loans | Commercial | Lease financing
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	1,688		1,688		1,074
ALLL for loans and leases individually evaluated for impairment	223		223		75
Impaired Financing Receivable, with Related Allowance, Recorded Investment	1,685		1,685		1,002
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	3		3		72
Financing Receivable, Individually Evaluated for Impairment	1,688		1,688		1,074
Average balance	1,752	1,169	1,744	1,347
Interest income recognized	12	14	40	49
Provision for Loan, Lease, and Other Losses	884	274	1,645	337
Financing Receivable, Allowance for Credit Losses, Write-downs	687	132	957	93
Recoveries	3	5	9	145
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	6,381		6,381		5,832
Financing Receivable, Collectively Evaluated for Impairment	865,116		865,116		825,196
Loans and Leases Receivable, Net Amount	866,804		866,804		826,270
Non-PCI Loans | Commercial | Other
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	522		522		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	522		522		0
Financing Receivable, Individually Evaluated for Impairment	522		522		142
Average balance	557	569	396	818
Interest income recognized	8	6	15	30
Provision for Loan, Lease, and Other Losses	58	183	299	(109)
Financing Receivable, Allowance for Credit Losses, Write-downs	666	0	853	22
Recoveries	123	170	244	384
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	2,817		2,817		3,104
Financing Receivable, Collectively Evaluated for Impairment	321,694		321,694		340,122
Loans and Leases Receivable, Net Amount	322,216		322,216		340,264
Non-PCI Loans | Noncommercial | Construction and land development
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	4,365		4,365		3,030
ALLL for loans and leases individually evaluated for impairment	94		94		109
Impaired Financing Receivable, with Related Allowance, Recorded Investment	781		781		645
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	2,879		2,879		1,968
Financing Receivable, Individually Evaluated for Impairment	3,660		3,660		2,613
Average balance	3,676	408	3,155	459
Interest income recognized	35	5	101	16
Provision for Loan, Lease, and Other Losses	92	88	(1)	253
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	1,501		1,501		1,487
Financing Receivable, Collectively Evaluated for Impairment	223,524		223,524		228,787
Loans and Leases Receivable, Net Amount	227,184		227,184		231,400
Non-PCI Loans | Noncommercial | Mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	33,712		33,712		32,588
ALLL for loans and leases individually evaluated for impairment	1,907		1,907		2,447
Impaired Financing Receivable, with Related Allowance, Recorded Investment	18,840		18,840		20,269
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	13,287		13,287		11,207
Financing Receivable, Individually Evaluated for Impairment	32,127		32,127		31,476
Average balance	31,290	28,008	33,673	25,497
Interest income recognized	228	214	753	564
Provision for Loan, Lease, and Other Losses	531	531	2,037	2,794
Financing Receivable, Allowance for Credit Losses, Write-downs	604	328	1,076	680
Recoveries	92	334	454	394
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	13,955		13,955		12,000
Financing Receivable, Collectively Evaluated for Impairment	3,435,851		3,435,851		2,857,648
Loans and Leases Receivable, Net Amount	3,467,978		3,467,978		2,889,124
Non-PCI Loans | Noncommercial | Revolving mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	20,403		20,403		8,831
ALLL for loans and leases individually evaluated for impairment	1,784		1,784		366
Impaired Financing Receivable, with Related Allowance, Recorded Investment	9,046		9,046		1,825
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	9,784		9,784		5,788
Financing Receivable, Individually Evaluated for Impairment	18,830		18,830		7,613
Average balance	18,066	7,373	11,506	6,701
Interest income recognized	150	48	269	120
Provision for Loan, Lease, and Other Losses	842	679	2,446	3,306
Financing Receivable, Allowance for Credit Losses, Write-downs	218	391	1,323	2,507
Recoveries	228	256	1,181	502
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	21,533		21,533		20,647
Financing Receivable, Collectively Evaluated for Impairment	2,673,728		2,673,728		2,593,731
Loans and Leases Receivable, Net Amount	2,692,558		2,692,558		2,601,344
Non-PCI Loans | Noncommercial | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Unpaid principal balance	2,445		2,445		2,086
ALLL for loans and leases individually evaluated for impairment	653		653		667
Impaired Financing Receivable, with Related Allowance, Recorded Investment	1,527		1,527		1,532
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	699		699		380
Financing Receivable, Individually Evaluated for Impairment	2,226		2,226		1,912
Average balance	2,233	1,507	2,062	1,398
Interest income recognized	27	20	74	58
Provision for Loan, Lease, and Other Losses	4,785	3,899	11,144	8,193
Financing Receivable, Allowance for Credit Losses, Write-downs	4,996	3,623	14,015	9,868
Recoveries	1,203	$ 1,092	3,376	$ 3,194
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	28,139		28,139		27,620
Financing Receivable, Collectively Evaluated for Impairment	1,509,261		1,509,261		1,444,226
Loans and Leases Receivable, Net Amount	$ 1,511,487		$ 1,511,487		$ 1,446,138