Loans and Leases - Age Analysis of Past Due Loans, by Class (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 14,896,943	$ 12,190,440
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	5,435,162	4,109,056
Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	3,042,781	2,601,722
Commercial Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	196,636	204,553
Total Commercial Loans and Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	8,674,579	6,915,331
Direct Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	1,844,399	1,706,636
Residential Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	1,844,574	1,395,971
Indirect Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	1,196,313	996,729
Consumer Lines of Credit [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	1,301,200	1,137,255
Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	35,878	38,518
Originated Loans and Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	59,850	46,683
> 90 Days Past Due and Still Accruing	9,113	7,024
Non-Accrual	62,083	48,774
Total Past Due	131,046	102,481
Current	12,416,941	10,929,498
Total Loans	12,547,987	11,031,979
Originated Loans and Leases [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	8,452	11,006
> 90 Days Past Due and Still Accruing	1	1
Non-Accrual	20,114	23,503
Total Past Due	28,567	34,510
Current	4,067,250	3,496,636
Total Loans	4,095,817	3,531,146
Originated Loans and Leases [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	16,019	5,409
> 90 Days Past Due and Still Accruing	3	3
Non-Accrual	24,141	14,382
Total Past Due	40,163	19,794
Current	2,671,723	2,514,557
Total Loans	2,711,886	2,534,351
Originated Loans and Leases [Member] | Commercial Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	973	924
> 90 Days Past Due and Still Accruing	1
Non-Accrual	3,429	659
Total Past Due	4,403	1,583
Current	192,233	202,970
Total Loans	196,636	204,553
Originated Loans and Leases [Member] | Total Commercial Loans and Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	25,444	17,339
> 90 Days Past Due and Still Accruing	5	4
Non-Accrual	47,684	38,544
Total Past Due	73,133	55,887
Current	6,931,206	6,214,163
Total Loans	7,004,339	6,270,050
Originated Loans and Leases [Member] | Direct Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	10,573	9,254
> 90 Days Past Due and Still Accruing	4,386	3,813
Non-Accrual	6,484	4,806
Total Past Due	21,443	17,873
Current	1,743,814	1,642,844
Total Loans	1,765,257	1,660,717
Originated Loans and Leases [Member] | Residential Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	10,594	8,135
> 90 Days Past Due and Still Accruing	3,014	1,470
Non-Accrual	3,316	2,882
Total Past Due	16,924	12,487
Current	1,429,852	1,032,202
Total Loans	1,446,776	1,044,689
Originated Loans and Leases [Member] | Indirect Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	9,312	9,472
> 90 Days Past Due and Still Accruing	513	379
Non-Accrual	1,983	1,361
Total Past Due	11,808	11,212
Current	1,184,302	984,963
Total Loans	1,196,110	996,175
Originated Loans and Leases [Member] | Consumer Lines of Credit [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	3,529	2,410
> 90 Days Past Due and Still Accruing	1,112	1,189
Non-Accrual	1,616	1,181
Total Past Due	6,257	4,780
Current	1,093,370	1,017,050
Total Loans	1,099,627	1,021,830
Originated Loans and Leases [Member] | Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	398	73
> 90 Days Past Due and Still Accruing	83	169
Non-Accrual	1,000
Total Past Due	1,481	242
Current	34,397	38,276
Total Loans	35,878	38,518
Acquired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	24,210	15,034
> 90 Days Past Due and Still Accruing	40,524	29,718
Non-Accrual	3,396	1,123
Total Past Due	68,130	45,875
Current	2,430,340	1,193,517
(Discount)/Premium	(149,514)	(80,931)
Total Loans	2,348,956	1,158,461
Acquired Loans [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	9,501	6,399
> 90 Days Past Due and Still Accruing	23,890	12,752
Non-Accrual	949	931
Total Past Due	34,340	20,082
Current	1,384,752	593,128
(Discount)/Premium	(79,747)	(35,300)
Total Loans	1,339,345	577,910
Acquired Loans [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	1,789	1,065
> 90 Days Past Due and Still Accruing	2,942	616
Non-Accrual	2,111	103
Total Past Due	6,842	1,784
Current	353,494	72,037
(Discount)/Premium	(29,441)	(6,450)
Total Loans	330,895	67,371
Acquired Loans [Member] | Total Commercial Loans and Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	11,290	7,464
> 90 Days Past Due and Still Accruing	26,832	13,368
Non-Accrual	3,060	1,034
Total Past Due	41,182	21,866
Current	1,738,246	665,165
(Discount)/Premium	(109,188)	(41,750)
Total Loans	1,670,240	645,281
Acquired Loans [Member] | Direct Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	2,317	837
> 90 Days Past Due and Still Accruing	1,344	659
Total Past Due	3,661	1,496
Current	73,479	43,596
(Discount)/Premium	2,002	827
Total Loans	79,142	45,919
Acquired Loans [Member] | Residential Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	8,428	5,871
> 90 Days Past Due and Still Accruing	10,816	15,136
Total Past Due	19,244	21,007
Current	416,561	366,742
(Discount)/Premium	(38,007)	(36,467)
Total Loans	397,798	351,282
Acquired Loans [Member] | Indirect Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	19	32
> 90 Days Past Due and Still Accruing	4	9
Total Past Due	23	41
Current	96	571
(Discount)/Premium	84	(58)
Total Loans	203	554
Acquired Loans [Member] | Consumer Lines of Credit [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	2,156	830
> 90 Days Past Due and Still Accruing	1,528	546
Non-Accrual	336	89
Total Past Due	4,020	1,465
Current	201,958	117,443
(Discount)/Premium	(4,405)	(3,483)
Total Loans	$ 201,573	$ 115,425