FAIR VALUES OF FINANCIAL INSTRUMENTS - Carrying Amounts and Estimated Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Financial assets
Cash and cash equivalents	$ 409,281	$ 439,510
Time deposits in financial institutions	1,000	1,000
Securities available-for-sale	2,434,541	2,381,488
Securities held-to-maturity	879,898	899,743
Federal Home Loan Bank and other bank stock	63,238	67,842
Loans held-for-sale	653,422	711,188
Loans and leases receivable, net of ALLL	6,067,839	5,999,791
Accrued interest receivable	35,051	36,382
Derivative assets	11,065	17,968
Financial liabilities
Deposits	8,373,201	8,908,406
Advances from Federal Home Loan Bank	1,079,952	490,351
Securities sold under repurchase agreements	26,320
Other borrowings	68,000	68,000
Long term debt	177,126	174,006
Derivative liabilities	4,086	2,116
Accrued interest payable	6,606	4,114
Discontinued Operations, Disposed of by Sale | Banc Home Loan
Financial liabilities
Loans held-for-sale, carried at fair value	420,449	406,338
Quoted Prices in Active Markets for Identical Assets (Level 1)
Financial assets
Cash and cash equivalents	409,281	439,510
Time deposits in financial institutions	1,000	1,000
Securities available-for-sale	0	0
Securities held-to-maturity	0	0
Federal Home Loan Bank and other bank stock	0	0
Loans held-for-sale	0	0
Loans and leases receivable, net of ALLL	0	0
Accrued interest receivable	35,051	36,382
Derivative assets	0	0
Financial liabilities
Deposits	0	0
Advances from Federal Home Loan Bank	0	0
Securities sold under repurchase agreements	0
Other borrowings	0	0
Long term debt	0	0
Derivative liabilities	0	0
Accrued interest payable	6,606	4,114
Quoted Prices in Active Markets for Identical Assets (Level 1) | Recurring
Financial assets
Loans held-for-sale	0	0
Significant Other Observable Inputs (Level 2)
Financial assets
Cash and cash equivalents	0	0
Time deposits in financial institutions	0	0
Securities available-for-sale	2,434,541	2,381,488
Securities held-to-maturity	879,898	899,743
Federal Home Loan Bank and other bank stock	63,238	67,842
Loans held-for-sale	586,721	652,928
Loans and leases receivable, net of ALLL	0	0
Accrued interest receivable	0	0
Derivative assets	11,065	17,968
Financial liabilities
Deposits	0	0
Advances from Federal Home Loan Bank	1,079,952	490,351
Securities sold under repurchase agreements	26,320
Other borrowings	68,000	68,000
Long term debt	177,126	174,006
Derivative liabilities	4,086	2,116
Accrued interest payable	0	0
Significant Other Observable Inputs (Level 2) | Recurring
Financial assets
Loans held-for-sale	355,443	358,714
Significant Other Observable Inputs (Level 2) | Recurring | Discontinued Operations, Disposed of by Sale | Banc Home Loan
Financial liabilities
Loans held-for-sale, carried at fair value	353,748	348,078
Significant Unobservable Inputs (Level 3)
Financial assets
Cash and cash equivalents	0	0
Time deposits in financial institutions	0	0
Securities available-for-sale	0	0
Securities held-to-maturity	0	0
Federal Home Loan Bank and other bank stock	0	0
Loans held-for-sale	66,701	58,260
Loans and leases receivable, net of ALLL	6,067,839	5,999,791
Accrued interest receivable	0	0
Derivative assets	0	0
Financial liabilities
Deposits	8,373,201	8,908,406
Advances from Federal Home Loan Bank	0	0
Securities sold under repurchase agreements	0
Other borrowings	0	0
Long term debt	0	0
Derivative liabilities	0	0
Accrued interest payable	0	0
Significant Unobservable Inputs (Level 3) | Recurring
Financial assets
Loans held-for-sale	66,701	58,260
Significant Unobservable Inputs (Level 3) | Recurring | Discontinued Operations, Disposed of by Sale | Banc Home Loan
Financial liabilities
Loans held-for-sale, carried at fair value	66,701	58,260
Carrying Value
Financial assets
Cash and cash equivalents	409,281	439,510
Time deposits in financial institutions	1,000	1,000
Securities available-for-sale	2,434,541	2,381,488
Securities held-to-maturity	863,269	884,234
Federal Home Loan Bank and other bank stock	63,238	67,842
Loans held-for-sale	649,327	704,651
Loans and leases receivable, net of ALLL	6,062,585	5,994,308
Accrued interest receivable	35,051	36,382
Derivative assets	11,065	17,968
Financial liabilities
Deposits	8,597,693	9,142,150
Advances from Federal Home Loan Bank	1,080,000	490,000
Securities sold under repurchase agreements	26,320
Other borrowings	67,981	67,922
Long term debt	174,090	175,378
Derivative liabilities	4,086	2,116
Accrued interest payable	6,606	4,114
Carrying Value | Recurring
Financial assets
Loans held-for-sale	$ 422,144	$ 416,974