Loans and Leases - Summary of Loans and Leases, Net of Unearned Income (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	$ 14,563,128	$ 12,190,440
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	5,355,625	4,109,056
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	3,079,605	2,601,722
Commercial Leases [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	200,350	204,553
Total Commercial Loans and Leases [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	8,635,580	6,915,331
Direct Installment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	1,830,206	1,706,636
Residential Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	1,678,646	1,395,971
Indirect Installment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	1,076,817	996,729
Consumer Lines of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	1,290,053	1,137,255
Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	51,826	38,518
Originated Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	11,770,152	11,031,979
Originated Loans [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	3,789,036	3,531,146
Originated Loans [Member] | Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	2,643,116	2,534,351
Originated Loans [Member] | Commercial Leases [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	200,350	204,553
Originated Loans [Member] | Total Commercial Loans and Leases [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	6,632,502	6,270,050
Originated Loans [Member] | Direct Installment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	1,733,606	1,660,717
Originated Loans [Member] | Residential Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	1,217,574	1,044,689
Originated Loans [Member] | Indirect Installment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	1,076,516	996,175
Originated Loans [Member] | Consumer Lines of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	1,058,128	1,021,830
Originated Loans [Member] | Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	51,826	38,518
Acquired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	2,792,976	1,158,461
Acquired Loans [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	1,566,589	577,910
Acquired Loans [Member] | Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	436,489	67,371
Acquired Loans [Member] | Total Commercial Loans and Leases [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	2,003,078	645,281
Acquired Loans [Member] | Direct Installment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	96,600	45,919
Acquired Loans [Member] | Residential Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	461,072	351,282
Acquired Loans [Member] | Indirect Installment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	301	554
Acquired Loans [Member] | Consumer Lines of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, net of unearned income	$ 231,925	$ 115,425