Loans and Leases - Summary of Loans and Leases, Net of Unearned Income (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	$ 12,190,440	$ 11,247,038
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	4,109,056	3,815,708
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	2,601,722	2,318,015
Commercial Leases [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	204,553	177,824
Total Commercial Loans and Leases [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	6,915,331	6,311,547
Direct Installment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	1,706,636	1,644,621
Residential Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	1,395,971	1,263,053
Indirect Installment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	996,729	875,551
Consumer Lines of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	1,137,255	1,110,976
Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	38,518	41,290
Originated Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	11,031,979	9,666,145
Originated Loans [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	3,531,146	3,031,810
Originated Loans [Member] | Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	2,534,351	2,197,793
Originated Loans [Member] | Commercial Leases [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	204,553	177,824
Originated Loans [Member] | Total Commercial Loans and Leases [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	6,270,050	5,407,427
Originated Loans [Member] | Direct Installment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	1,660,717	1,579,770
Originated Loans [Member] | Residential Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	1,044,689	817,586
Originated Loans [Member] | Indirect Installment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	996,175	873,645
Originated Loans [Member] | Consumer Lines of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	1,021,830	946,427
Originated Loans [Member] | Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	38,518	41,290
Acquired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	1,158,461	1,580,893
Acquired Loans [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	577,910	783,898
Acquired Loans [Member] | Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	67,371	120,222
Acquired Loans [Member] | Total Commercial Loans and Leases [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	645,281	904,120
Acquired Loans [Member] | Direct Installment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	45,919	64,851
Acquired Loans [Member] | Residential Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	351,282	445,467
Acquired Loans [Member] | Indirect Installment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	554	1,906
Acquired Loans [Member] | Consumer Lines of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	$ 115,425	$ 164,549