Credit Risk Profile by Risk Rating - Originated and Non-PCI Loans (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	$ 11,631,628	$ 11,280,513	$ 10,848,578
Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	4,637,009	4,553,040
Commercial [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	4,637,009	4,553,040
Asset-based [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	368,328	336,614
Asset-based [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	368,328	336,614
Factoring [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	249,351	221,672
Factoring [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	249,351	221,672
Real estate - construction [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	789,458	717,849
Real estate - commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	3,748,626	3,563,630
Real estate - commercial [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	3,748,626	3,563,630
Non-watch list [Member] | Commercial [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	4,142,433	4,048,238
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	291,213	306,899
Non-watch list [Member] | Factoring [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	249,163	220,795
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	787,424	716,830
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	3,594,253	3,434,982
Watch [Member] | Commercial [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	161,466	162,788
Watch [Member] | Real estate - construction [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	1,841	631
Watch [Member] | Real estate - commercial [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	55,776	50,715
Special Mention [Member] | Commercial [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	117,253	106,638
Special Mention [Member] | Asset-based [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	77,115	29,715
Special Mention [Member] | Factoring [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	188	47
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	34,051	35,940
Substandard [Member] | Commercial [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	215,857	235,376
Substandard [Member] | Factoring [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating		830
Substandard [Member] | Real estate - construction [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	193	388
Substandard [Member] | Real estate - commercial [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	$ 64,546	$ 41,993