Loans and Leases - Age Analysis of Past Due Loans, by Class (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 14,563,128	$ 12,190,440
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	5,355,625	4,109,056
Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	3,079,605	2,601,722
Commercial Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	200,350	204,553
Total Commercial Loans and Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	8,635,580	6,915,331
Direct Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	1,830,206	1,706,636
Residential Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	1,678,646	1,395,971
Indirect Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	1,076,817	996,729
Consumer Lines of Credit [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	1,290,053	1,137,255
Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	51,826	38,518
Originated Loans and Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	48,706	46,683
> 90 Days Past Due and Still Accruing	6,186	7,024
Non-Accrual	64,998	48,774
Total Past Due	119,890	102,481
Current	11,650,262	10,929,498
Total Loans	11,770,152	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	9,219	11,006
> 90 Days Past Due and Still Accruing	1	1
Non-Accrual	23,797	23,503
Total Past Due	33,017	34,510
Current	3,756,019	3,496,636
Total Loans	3,789,036	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	9,411	5,409
> 90 Days Past Due and Still Accruing	3	3
Non-Accrual	27,568	14,382
Total Past Due	36,982	19,794
Current	2,606,134	2,514,557
Total Loans	2,643,116	2,534,351
Originated Loans and Leases [Member] | Commercial Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	1,099	924
Non-Accrual	1,142	659
Total Past Due	2,241	1,583
Current	198,109	202,970
Total Loans	200,350	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	19,729	17,339
> 90 Days Past Due and Still Accruing	4	4
Non-Accrual	52,507	38,544
Total Past Due	72,240	55,887
Current	6,560,262	6,214,163
Total Loans	6,632,502	6,270,050
Originated Loans and Leases [Member] | Direct Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	9,479	9,254
> 90 Days Past Due and Still Accruing	3,690	3,813
Non-Accrual	5,743	4,806
Total Past Due	18,912	17,873
Current	1,714,694	1,642,844
Total Loans	1,733,606	1,660,717
Originated Loans and Leases [Member] | Residential Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	11,249	8,135
> 90 Days Past Due and Still Accruing	1,662	1,470
Non-Accrual	3,072	2,882
Total Past Due	15,983	12,487
Current	1,201,591	1,032,202
Total Loans	1,217,574	1,044,689
Originated Loans and Leases [Member] | Indirect Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	6,067	9,472
> 90 Days Past Due and Still Accruing	270	379
Non-Accrual	1,613	1,361
Total Past Due	7,950	11,212
Current	1,068,566	984,963
Total Loans	1,076,516	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	2,141	2,410
> 90 Days Past Due and Still Accruing	532	1,189
Non-Accrual	2,063	1,181
Total Past Due	4,736	4,780
Current	1,053,392	1,017,050
Total Loans	1,058,128	1,021,830
Originated Loans and Leases [Member] | Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	41	73
> 90 Days Past Due and Still Accruing	28	169
Total Past Due	69	242
Current	51,757	38,276
Total Loans	51,826	38,518
Acquired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	42,939	15,034
> 90 Days Past Due and Still Accruing	47,085	29,718
Non-Accrual	2,477	1,123
Total Past Due	92,501	45,875
Current	2,863,034	1,193,517
Discount	(162,559)	(80,931)
Total Loans	2,792,976	1,158,461
Acquired Loans [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	24,253	6,399
> 90 Days Past Due and Still Accruing	26,315	12,752
Non-Accrual	893	931
Total Past Due	51,461	20,082
Current	1,602,228	593,128
Discount	(87,100)	(35,300)
Total Loans	1,566,589	577,910
Acquired Loans [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	2,758	1,065
> 90 Days Past Due and Still Accruing	4,821	616
Non-Accrual	1,163	103
Total Past Due	8,742	1,784
Current	461,688	72,037
Discount	(33,941)	(6,450)
Total Loans	436,489	67,371
Acquired Loans [Member] | Total Commercial Loans and Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	27,011	7,464
> 90 Days Past Due and Still Accruing	31,136	13,368
Non-Accrual	2,056	1,034
Total Past Due	60,203	21,866
Current	2,063,916	665,165
Discount	(121,041)	(41,750)
Total Loans	2,003,078	645,281
Acquired Loans [Member] | Direct Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	2,602	837
> 90 Days Past Due and Still Accruing	1,124	659
Total Past Due	3,726	1,496
Current	90,263	43,596
Discount	2,611	827
Total Loans	96,600	45,919
Acquired Loans [Member] | Residential Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	11,990	5,871
> 90 Days Past Due and Still Accruing	13,963	15,136
Total Past Due	25,953	21,007
Current	474,442	366,742
Discount	(39,323)	(36,467)
Total Loans	461,072	351,282
Acquired Loans [Member] | Indirect Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	11	32
> 90 Days Past Due and Still Accruing	4	9
Total Past Due	15	41
Current	255	571
Discount	31	(58)
Total Loans	301	554
Acquired Loans [Member] | Consumer Lines of Credit [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	1,325	830
> 90 Days Past Due and Still Accruing	858	546
Non-Accrual	421	89
Total Past Due	2,604	1,465
Current	234,158	117,443
Discount	(4,837)	(3,483)
Total Loans	$ 231,925	$ 115,425