Credit Risk Profile by Risk Rating - Originated and Non-PCI Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	$ 11,280,513	$ 10,540,383	$ 9,430,761
Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	4,553,040	4,410,806
Commercial [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	4,553,040	4,410,806
Asset-based [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	336,614	225,878
Asset-based [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	336,614	225,878
Factoring [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	221,672	139,902
Factoring [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	221,672	139,902
Real estate - construction [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	717,849	741,804
Real estate - commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	3,563,630	3,165,922
Real estate - commercial [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	3,563,630	3,165,922
Non-watch list [Member] | Commercial [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	4,048,238	4,043,704
Non-watch list [Member] | Asset-based [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	306,899	198,695
Non-watch list [Member] | Factoring [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	220,795	139,358
Non-watch list [Member] | Real estate - construction [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	716,830	741,022
Non-watch list [Member] | Real estate - commercial [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	3,434,982	3,071,804
Watch [Member] | Commercial [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	162,788	99,815
Watch [Member] | Real estate - construction [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	631	149
Watch [Member] | Real estate - commercial [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	50,715	43,015
Special Mention [Member] | Commercial [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	106,638	32,240
Special Mention [Member] | Asset-based [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	29,715	24,809
Special Mention [Member] | Factoring [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	47	129
Special Mention [Member] | Real estate - commercial [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	35,940	5,140
Substandard [Member] | Commercial [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	235,376	235,047
Substandard [Member] | Asset-based [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating		2,374
Substandard [Member] | Factoring [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	830	415
Substandard [Member] | Real estate - construction [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	388	633
Substandard [Member] | Real estate - commercial [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	$ 41,993	$ 45,963