Credit Risk Profile by Risk Rating - Originated and Non-PCI Loans (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	$ 11,964,724	$ 11,280,513	$ 10,997,028
Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	4,907,199	4,553,040
Commercial [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	4,907,199	4,553,040
Asset-based [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	391,875	336,614
Asset-based [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	391,875	336,614
Factoring [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	287,352	221,672
Factoring [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	287,352	221,672
Real estate - construction [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	828,033	717,849
Real estate - commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	3,717,154	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	3,717,154	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	4,447,646	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	329,986	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	245,248	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	827,835	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	3,581,155	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	158,164	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		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	48,567	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	68,591	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	59,396	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	42,104	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	20,869	35,940
Substandard [Member] | Commercial [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	232,798	235,376
Substandard [Member] | Asset-based [Member] | Originated and Non-PCI Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile by Risk Rating	2,493
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	198	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	$ 66,563	$ 41,993