FAIR VALUES OF FINANCIAL INSTRUMENTS - Recurring Basis (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	$ 1,941,588		$ 833,596
Loans held-for-sale	856,593		672,850
Derivative assets	15,746		9,042
Mortgage servicing rights, at fair value	62,676	$ 52,567	49,939	$ 40,837	$ 34,198	$ 19,082
Derivative liabilities	4,650		1,067
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0		0
Loans held-for-sale	0		0
Derivative assets	0		0
Derivative liabilities	0		0
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	1,941,588		833,596
Loans held-for-sale	808,945		654,559
Derivative assets	15,746		9,042
Derivative liabilities	4,650		1,067
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0		0
Loans held-for-sale	47,648		18,291
Derivative assets	0		0
Derivative liabilities	0		0
Carrying Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	1,941,588		833,596
Loans held-for-sale	846,844		668,841
Derivative assets	15,746		9,042
Derivative liabilities	4,650		1,067
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale	0		0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | SBA loan pool securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0		0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Private label residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0		0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0		0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Collateralized loan obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0		0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Agency mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0		0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0		0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Servicing Asset
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage servicing rights, at fair value	0		0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Accrued Expenses and Other Liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	0		0
Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale	450,406		360,864
Recurring | Significant Other Observable Inputs (Level 2) | SBA loan pool securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	1,265		1,504
Recurring | Significant Other Observable Inputs (Level 2) | Private label residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	117,112		1,768
Recurring | Significant Other Observable Inputs (Level 2) | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	73,596		26,152
Recurring | Significant Other Observable Inputs (Level 2) | Collateralized loan obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	1,334,002		111,468
Recurring | Significant Other Observable Inputs (Level 2) | Agency mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	415,613		692,704
Recurring | Significant Other Observable Inputs (Level 2) | Other Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	15,746		9,042
Recurring | Significant Other Observable Inputs (Level 2) | Servicing Asset
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage servicing rights, at fair value	0		0
Recurring | Significant Other Observable Inputs (Level 2) | Accrued Expenses and Other Liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	4,650		1,067
Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale	47,648		18,291
Recurring | Significant Unobservable Inputs (Level 3) | SBA loan pool securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0		0
Recurring | Significant Unobservable Inputs (Level 3) | Private label residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0		0
Recurring | Significant Unobservable Inputs (Level 3) | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0		0
Recurring | Significant Unobservable Inputs (Level 3) | Collateralized loan obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0		0
Recurring | Significant Unobservable Inputs (Level 3) | Agency mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0		0
Recurring | Significant Unobservable Inputs (Level 3) | Other Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0		0
Recurring | Significant Unobservable Inputs (Level 3) | Servicing Asset
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage servicing rights, at fair value	62,676		49,939
Recurring | Significant Unobservable Inputs (Level 3) | Accrued Expenses and Other Liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	0		0
Recurring | Carrying Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale	498,054		379,155
Recurring | Carrying Value | SBA loan pool securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	1,265		1,504
Recurring | Carrying Value | Private label residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	117,112		1,768
Recurring | Carrying Value | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	73,596		26,152
Recurring | Carrying Value | Collateralized loan obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	1,334,002		111,468
Recurring | Carrying Value | Agency mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	415,613		692,704
Recurring | Carrying Value | Other Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	15,746		9,042
Recurring | Carrying Value | Servicing Asset
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage servicing rights, at fair value	62,676		49,939
Recurring | Carrying Value | Accrued Expenses and Other Liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	$ 4,650		$ 1,067