Loans and Leases - Age Analysis of Past Due Loans, by Class (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 12,190,440	$ 11,247,038
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	4,109,056	3,815,708
Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	2,601,722	2,318,015
Commercial Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	204,553	177,824
Total Commercial Loans and Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	6,915,331	6,311,547
Direct Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	1,706,636	1,644,621
Residential Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	1,395,971	1,263,053
Indirect Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	996,729	875,551
Consumer Lines of Credit [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	1,137,255	1,110,976
Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	38,518	41,290
Originated Loans and Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	46,683	41,275
> 90 Days Past Due and Still Accruing	7,024	9,248
Non-Accrual	48,774	45,113
Total Past Due	102,481	95,636
Current	10,929,498	9,570,509
Total Loans	11,031,979	9,666,145
Originated Loans and Leases [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	11,006	9,601
> 90 Days Past Due and Still Accruing	1	313
Non-Accrual	23,503	24,132
Total Past Due	34,510	34,046
Current	3,496,636	2,997,764
Total Loans	3,531,146	3,031,810
Originated Loans and Leases [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	5,409	2,446
> 90 Days Past Due and Still Accruing	3	3
Non-Accrual	14,382	8,310
Total Past Due	19,794	10,759
Current	2,514,557	2,187,034
Total Loans	2,534,351	2,197,793
Originated Loans and Leases [Member] | Commercial Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	924	961
> 90 Days Past Due and Still Accruing		43
Non-Accrual	659	722
Total Past Due	1,583	1,726
Current	202,970	176,098
Total Loans	204,553	177,824
Originated Loans and Leases [Member] | Total Commercial Loans and Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	17,339	13,008
> 90 Days Past Due and Still Accruing	4	359
Non-Accrual	38,544	33,164
Total Past Due	55,887	46,531
Current	6,214,163	5,360,896
Total Loans	6,270,050	5,407,427
Originated Loans and Leases [Member] | Direct Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	9,254	9,333
> 90 Days Past Due and Still Accruing	3,813	3,617
Non-Accrual	4,806	7,117
Total Past Due	17,873	20,067
Current	1,642,844	1,559,703
Total Loans	1,660,717	1,579,770
Originated Loans and Leases [Member] | Residential Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	8,135	8,709
> 90 Days Past Due and Still Accruing	1,470	3,891
Non-Accrual	2,882	2,964
Total Past Due	12,487	15,564
Current	1,032,202	802,022
Total Loans	1,044,689	817,586
Originated Loans and Leases [Member] | Indirect Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	9,472	7,804
> 90 Days Past Due and Still Accruing	379	684
Non-Accrual	1,361	1,149
Total Past Due	11,212	9,637
Current	984,963	864,008
Total Loans	996,175	873,645
Originated Loans and Leases [Member] | Consumer Lines of Credit [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	2,410	2,408
> 90 Days Past Due and Still Accruing	1,189	562
Non-Accrual	1,181	719
Total Past Due	4,780	3,689
Current	1,017,050	942,738
Total Loans	1,021,830	946,427
Originated Loans and Leases [Member] | Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	73	13
> 90 Days Past Due and Still Accruing	169	135
Total Past Due	242	148
Current	38,276	41,142
Total Loans	38,518	41,290
Acquired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	15,034	24,678
> 90 Days Past Due and Still Accruing	29,718	38,024
Non-Accrual	1,123
Total Past Due	45,875	62,702
Current	1,193,517	1,612,959
Discount	(80,931)	(94,768)
Total Loans	1,158,461	1,580,893
Acquired Loans [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	6,399	12,076
> 90 Days Past Due and Still Accruing	12,752	12,368
Non-Accrual	931
Total Past Due	20,082	24,444
Current	593,128	799,991
Discount	(35,300)	(40,537)
Total Loans	577,910	783,898
Acquired Loans [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	1,065	687
> 90 Days Past Due and Still Accruing	616	1,968
Non-Accrual	103
Total Past Due	1,784	2,655
Current	72,037	127,535
Discount	(6,450)	(9,968)
Total Loans	67,371	120,222
Acquired Loans [Member] | Total Commercial Loans and Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	7,464	12,763
> 90 Days Past Due and Still Accruing	13,368	14,336
Non-Accrual	1,034
Total Past Due	21,866	27,099
Current	665,165	927,526
Discount	(41,750)	(50,505)
Total Loans	645,281	904,120
Acquired Loans [Member] | Direct Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	837	2,670
> 90 Days Past Due and Still Accruing	659	1,443
Total Past Due	1,496	4,113
Current	43,596	59,532
Discount	827	1,206
Total Loans	45,919	64,851
Acquired Loans [Member] | Residential Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	5,871	8,159
> 90 Days Past Due and Still Accruing	15,136	19,936
Total Past Due	21,007	28,095
Current	366,742	456,810
Discount	(36,467)	(39,438)
Total Loans	351,282	445,467
Acquired Loans [Member] | Indirect Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	32	38
> 90 Days Past Due and Still Accruing	9	30
Total Past Due	41	68
Current	571	2,179
Discount	(58)	(341)
Total Loans	554	1,906
Acquired Loans [Member] | Consumer Lines of Credit [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	830	1,048
> 90 Days Past Due and Still Accruing	546	2,279
Non-Accrual	89
Total Past Due	1,465	3,327
Current	117,443	166,912
Discount	(3,483)	(5,690)
Total Loans	$ 115,425	$ 164,549