Loans and Allowance for Loan Losses - Age Analysis of Past Due Loans, by Class (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 10,333,873	$ 9,506,094
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	3,577,933	3,245,209
Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	2,103,896	1,881,474
Commercial Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	164,676	158,895
Total Commercial Loans and Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	5,846,505	5,285,578
Direct Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	1,512,149	1,467,236
Residential Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	1,145,286	1,086,739
Indirect Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	729,513	655,587
Consumer Lines of Credit [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	1,037,519	965,771
Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	62,901	45,183
Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	33,822	37,342
> 90 Days Past Due and Still Accruing	6,281	7,971
Non- Accrual	59,549	58,755
Total Past Due	99,652	104,068
Current	8,730,427	8,050,697
Total Loans	8,830,079	8,154,765
Originated Loans [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	5,313	5,428
> 90 Days Past Due and Still Accruing	157	252
Non- Accrual	39,300	40,960
Total Past Due	44,770	46,640
Current	2,796,066	2,593,788
Total Loans	2,840,836	2,640,428
Originated Loans [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	2,444	2,066
> 90 Days Past Due and Still Accruing	4	8
Non- Accrual	8,890	6,643
Total Past Due	11,338	8,717
Current	1,985,670	1,752,951
Total Loans	1,997,008	1,761,668
Originated Loans [Member] | Commercial Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	802	714
> 90 Days Past Due and Still Accruing
Non- Accrual	788	734
Total Past Due	1,590	1,448
Current	163,086	157,447
Total Loans	164,676	158,895
Originated Loans [Member] | Total Commercial Loans and Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	8,559	8,208
> 90 Days Past Due and Still Accruing	161	260
Non- Accrual	48,978	48,337
Total Past Due	57,698	56,805
Current	4,944,822	4,504,186
Total Loans	5,002,520	4,560,991
Originated Loans [Member] | Direct Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	9,158	9,038
> 90 Days Past Due and Still Accruing	3,118	3,753
Non- Accrual	4,846	4,686
Total Past Due	17,122	17,477
Current	1,421,225	1,370,518
Total Loans	1,438,347	1,387,995
Originated Loans [Member] | Residential Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	9,053	12,681
> 90 Days Past Due and Still Accruing	2,098	2,401
Non- Accrual	3,829	4,260
Total Past Due	14,980	19,342
Current	703,352	658,885
Total Loans	718,332	678,227
Originated Loans [Member] | Indirect Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	4,734	5,653
> 90 Days Past Due and Still Accruing	235	471
Non- Accrual	1,229	1,060
Total Past Due	6,198	7,184
Current	719,868	642,517
Total Loans	726,066	649,701
Originated Loans [Member] | Consumer Lines of Credit [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	2,293	1,737
> 90 Days Past Due and Still Accruing	662	1,076
Non- Accrual	667	412
Total Past Due	3,622	3,225
Current	878,291	829,443
Total Loans	881,913	832,668
Originated Loans [Member] | Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	25	25
> 90 Days Past Due and Still Accruing	7	10
Non- Accrual
Total Past Due	32	35
Current	62,869	45,148
Total Loans	62,901	45,183
Acquired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	30,656	30,205
> 90 Days Past Due and Still Accruing	58,636	45,823
Non- Accrual
Total Past Due	89,292	76,028
Current	1,512,184	1,373,199
Discount	(97,682)	(97,898)
Total Loans	1,503,794	1,351,329
Acquired Loans [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	15,322	13,637
> 90 Days Past Due and Still Accruing	30,769	20,668
Non- Accrual
Total Past Due	46,091	34,305
Current	740,533	619,197
Discount	(49,527)	(48,721)
Total Loans	737,097	604,781
Acquired Loans [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	1,068	1,860
> 90 Days Past Due and Still Accruing	5,373	1,899
Non- Accrual
Total Past Due	6,441	3,759
Current	108,955	124,415
Discount	(8,508)	(8,368)
Total Loans	106,888	119,806
Acquired Loans [Member] | Commercial Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due
> 90 Days Past Due and Still Accruing
Non- Accrual
Total Past Due
Current
Discount
Total Loans
Acquired Loans [Member] | Total Commercial Loans and Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	16,390	15,497
> 90 Days Past Due and Still Accruing	36,142	22,567
Non- Accrual
Total Past Due	52,532	38,064
Current	849,488	743,612
Discount	(58,035)	(57,089)
Total Loans	843,985	724,587
Acquired Loans [Member] | Direct Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	2,063	1,447
> 90 Days Past Due and Still Accruing	1,177	1,178
Non- Accrual
Total Past Due	3,240	2,625
Current	68,762	74,917
Discount	1,800	1,699
Total Loans	73,802	79,241
Acquired Loans [Member] | Residential Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	11,502	11,464
> 90 Days Past Due and Still Accruing	18,239	19,298
Non- Accrual
Total Past Due	29,741	30,762
Current	430,993	412,704
Discount	(33,780)	(34,954)
Total Loans	426,954	408,512
Acquired Loans [Member] | Indirect Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	54	205
> 90 Days Past Due and Still Accruing	39	31
Non- Accrual
Total Past Due	93	236
Current	3,874	6,267
Discount	(520)	(617)
Total Loans	3,447	5,886
Acquired Loans [Member] | Consumer Lines of Credit [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	647	1,592
> 90 Days Past Due and Still Accruing	3,039	2,749
Non- Accrual
Total Past Due	3,686	4,341
Current	159,067	135,699
Discount	(7,147)	(6,937)
Total Loans	155,606	133,103
Acquired Loans [Member] | Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due
> 90 Days Past Due and Still Accruing
Non- Accrual
Total Past Due
Current
Discount
Total Loans