Loans and Leases - Age Analysis of Past Due Loans, by Class (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 14,165,599	$ 12,190,440
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	5,253,660	4,109,056
Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	3,046,267	2,601,722
Commercial Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	202,605	204,553
Total Commercial Loans and Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	8,502,532	6,915,331
Direct Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	1,790,802	1,706,636
Residential Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	1,531,379	1,395,971
Indirect Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	1,025,727	996,729
Consumer Lines of Credit [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	1,261,493	1,137,255
Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	53,666	38,518
Originated Loans and Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	36,711	46,683
> 90 Days Past Due and Still Accruing	6,120	7,024
Non-Accrual	61,997	48,774
Total Past Due	104,828	102,481
Current	11,182,876	10,929,498
Total Loans	11,287,704	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	9,342	11,006
> 90 Days Past Due and Still Accruing	1	1
Non-Accrual	24,083	23,503
Total Past Due	33,426	34,510
Current	3,571,875	3,496,636
Total Loans	3,605,301	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	4,653	5,409
> 90 Days Past Due and Still Accruing	3	3
Non-Accrual	24,627	14,382
Total Past Due	29,283	19,794
Current	2,545,038	2,514,557
Total Loans	2,574,321	2,534,351
Originated Loans and Leases [Member] | Commercial Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	1,422	924
> 90 Days Past Due and Still Accruing	15
Non-Accrual	894	659
Total Past Due	2,331	1,583
Current	200,274	202,970
Total Loans	202,605	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	15,417	17,339
> 90 Days Past Due and Still Accruing	19	4
Non-Accrual	49,604	38,544
Total Past Due	65,040	55,887
Current	6,317,187	6,214,163
Total Loans	6,382,227	6,270,050
Originated Loans and Leases [Member] | Direct Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	6,845	9,254
> 90 Days Past Due and Still Accruing	3,463	3,813
Non-Accrual	5,646	4,806
Total Past Due	15,954	17,873
Current	1,670,083	1,642,844
Total Loans	1,686,037	1,660,717
Originated Loans and Leases [Member] | Residential Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	7,398	8,135
> 90 Days Past Due and Still Accruing	1,545	1,470
Non-Accrual	3,446	2,882
Total Past Due	12,389	12,487
Current	1,093,291	1,032,202
Total Loans	1,105,680	1,044,689
Originated Loans and Leases [Member] | Indirect Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	5,479	9,472
> 90 Days Past Due and Still Accruing	369	379
Non-Accrual	1,347	1,361
Total Past Due	7,195	11,212
Current	1,018,218	984,963
Total Loans	1,025,413	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	1,523	2,410
> 90 Days Past Due and Still Accruing	661	1,189
Non-Accrual	1,954	1,181
Total Past Due	4,138	4,780
Current	1,030,543	1,017,050
Total Loans	1,034,681	1,021,830
Originated Loans and Leases [Member] | Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	49	73
> 90 Days Past Due and Still Accruing	63	169
Total Past Due	112	242
Current	53,554	38,276
Total Loans	53,666	38,518
Acquired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	44,651	15,034
> 90 Days Past Due and Still Accruing	47,913	29,718
Non-Accrual	1,039	1,123
Total Past Due	93,603	45,875
Current	2,959,300	1,193,517
Discount	(175,008)	(80,931)
Total Loans	2,877,895	1,158,461
Acquired Loans [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	27,329	6,399
> 90 Days Past Due and Still Accruing	23,563	12,752
Non-Accrual	740	931
Total Past Due	51,632	20,082
Current	1,695,949	593,128
Discount	(99,222)	(35,300)
Total Loans	1,648,359	577,910
Acquired Loans [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	1,879	1,065
> 90 Days Past Due and Still Accruing	6,596	616
Non-Accrual	152	103
Total Past Due	8,627	1,784
Current	499,764	72,037
Discount	(36,445)	(6,450)
Total Loans	471,946	67,371
Acquired Loans [Member] | Total Commercial Loans and Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	29,208	7,464
> 90 Days Past Due and Still Accruing	30,159	13,368
Non-Accrual	892	1,034
Total Past Due	60,259	21,866
Current	2,195,713	665,165
Discount	(135,667)	(41,750)
Total Loans	2,120,305	645,281
Acquired Loans [Member] | Direct Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	2,855	837
> 90 Days Past Due and Still Accruing	958	659
Total Past Due	3,813	1,496
Current	97,964	43,596
Discount	2,988	827
Total Loans	104,765	45,919
Acquired Loans [Member] | Residential Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	11,010	5,871
> 90 Days Past Due and Still Accruing	15,498	15,136
Total Past Due	26,508	21,007
Current	436,528	366,742
Discount	(37,337)	(36,467)
Total Loans	425,699	351,282
Acquired Loans [Member] | Indirect Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due		32
> 90 Days Past Due and Still Accruing	6	9
Total Past Due	6	41
Current	413	571
Discount	(105)	(58)
Total Loans	314	554
Acquired Loans [Member] | Consumer Lines of Credit [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	1,578	830
> 90 Days Past Due and Still Accruing	1,292	546
Non-Accrual	147	89
Total Past Due	3,017	1,465
Current	228,682	117,443
Discount	(4,887)	(3,483)
Total Loans	$ 226,812	$ 115,425