LOAN PORTFOLIO - Corporation's Aging of Loans Held for Investment Portfolio (Detail) - USD ($) $ in Thousands	Sep. 30, 2016		Jun. 30, 2016	Dec. 31, 2015		Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2014
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	$ 920,393			$ 841,188
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Carrying Amount	168,141		$ 169,690	173,913		$ 176,085	$ 178,494	$ 102,604
Financing Receivable, Current	7,775,120			8,097,281
Loans held for investment	8,863,654			9,112,382		$ 9,140,462
90 days past due and still accruing	110,538	[1]		139,987	[2]
Financing Receivables 60 To 89 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	118,315			164,889
Financing Receivables 30 To 59 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	124,828			93,539
Financing Receivables Equal To Greater Than 90 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	677,250	[3]		582,760	[4]
Fha Va And Other Government Guaranteed Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	86,987	[1],[5],[6]		96,216	[2],[7],[8]
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Carrying Amount	0	[1],[5],[6]		0	[2],[7],[8]
Financing Receivable, Current	44,949	[1],[5],[6]		46,925	[2],[7],[8]
Loans held for investment	131,936	[1],[5],[6]		143,141	[2],[7],[8]
90 days past due and still accruing	81,677	[1],[5],[6]		90,168	[2],[7],[8]
Fha Va And Other Government Guaranteed Loans [Member] | Financing Receivables 60 To 89 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	5,310	[1],[5],[6]		6,048	[2],[7],[8]
Fha Va And Other Government Guaranteed Loans [Member] | Financing Receivables 30 To 59 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	0	[1],[5],[6]		0	[2],[7],[8]
Fha Va And Other Government Guaranteed Loans [Member] | Financing Receivables Equal To Greater Than 90 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	81,677	[1],[3],[5],[6]		90,168	[2],[4],[7],[8]
Residential Mortgage [Member]
Accounts Notes And Loans Receivable [Line Items]
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Carrying Amount	165,014	[5]		170,766	[7]
Loans held for investment	3,299,942			3,344,719
Commercial And Industrial [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	183,951			162,882
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Carrying Amount	0			0
Financing Receivable, Current	1,983,060			2,083,631
Loans held for investment	2,167,011			2,246,513
90 days past due and still accruing	1,468	[1]		13,842	[2]
Commercial And Industrial [Member] | Financing Receivables 60 To 89 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	500			6,412
Commercial And Industrial [Member] | Financing Receivables 30 To 59 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	44,967			5,577
Commercial And Industrial [Member] | Financing Receivables Equal To Greater Than 90 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	138,484	[3]		150,893	[4]
Commercial Mortgage Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	199,676	[5]		88,534	[7]
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Carrying Amount	3,127	[5]		3,147	[7]
Financing Receivable, Current	1,342,211	[5]		1,446,125	[7]
Loans held for investment	1,545,014	[5]		1,537,806	[7]
90 days past due and still accruing	4,791	[1],[5]		12,472	[2],[7]
Commercial Mortgage Loans [Member] | Financing Receivables 60 To 89 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	3,436	[5]		24,729	[7]
Commercial Mortgage Loans [Member] | Financing Receivables 30 To 59 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	0	[5]		0	[7]
Commercial Mortgage Loans [Member] | Financing Receivables Equal To Greater Than 90 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	196,240	[3],[5]		63,805	[4],[7]
Construction Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	124,298			156,195
Auto loans [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	91,828			105,058
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Carrying Amount	0			0
Financing Receivable, Current	766,969			829,922
Loans held for investment	858,797			934,980
90 days past due and still accruing	0	[1]		0	[2]
Auto loans [Member] | Financing Receivables 60 To 89 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	13,743			16,787
Auto loans [Member] | Financing Receivables 30 To 59 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	63,470			70,836
Auto loans [Member] | Financing Receivables Equal To Greater Than 90 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	14,615	[3]		17,435	[4]
Finance Leases [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	12,480			13,223
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Carrying Amount	0			0
Financing Receivable, Current	217,097			215,942
Loans held for investment	229,577			229,165
90 days past due and still accruing	0	[1]		0	[2]
Finance Leases [Member] | Financing Receivables 60 To 89 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	2,312			3,100
Finance Leases [Member] | Financing Receivables 30 To 59 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	8,199			7,664
Finance Leases [Member] | Financing Receivables Equal To Greater Than 90 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	1,969	[3]		2,459	[4]
Consumer Loan [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	25,822			30,110
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Carrying Amount	0			0
Financing Receivable, Current	613,193			632,894
Loans held for investment	639,015			663,004
90 days past due and still accruing	4,111	[1]		4,266	[2]
Consumer Loan [Member] | Financing Receivables 60 To 89 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	4,824			5,524
Consumer Loan [Member] | Financing Receivables 30 To 59 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	8,192			9,462
Consumer Loan [Member] | Financing Receivables Equal To Greater Than 90 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	12,806	[3]		15,124	[4]
Commercial Construction [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	36,953	[5]		51,188
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Carrying Amount	0	[5]		0	[7]
Financing Receivable, Current	38,460	[5]		32,142
Loans held for investment	75,413	[5]		83,330
90 days past due and still accruing	0	[1],[5]		0	[2]
Commercial Construction [Member] | Financing Receivables 60 To 89 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	0	[5]		11,722
Commercial Construction [Member] | Financing Receivables 30 To 59 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	0	[5]		0
Commercial Construction [Member] | Financing Receivables Equal To Greater Than 90 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	36,953	[3],[5]		39,466	[4]
Residential Construction [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	2,721	[5]		6,042	[7]
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Carrying Amount	0	[5]		0	[7]
Financing Receivable, Current	12,767	[5]		14,949	[7]
Loans held for investment	15,488	[5]		20,991	[7]
90 days past due and still accruing	668	[1],[5]		3,046	[2],[7]
Residential Construction [Member] | Financing Receivables 60 To 89 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	0	[5]		0	[7]
Residential Construction [Member] | Financing Receivables 30 To 59 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	0	[5]		0	[7]
Residential Construction [Member] | Financing Receivables Equal To Greater Than 90 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	2,721	[3],[5]		6,042	[4],[7]
Land Construction [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	12,902	[5]		12,511	[7]
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Carrying Amount	0			0	[7]
Financing Receivable, Current	20,495	[5]		39,363	[7]
Loans held for investment	33,397	[5]		51,874	[7]
90 days past due and still accruing	376	[1],[5]		176	[2],[7]
Land Construction [Member] | Financing Receivables 60 To 89 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	765	[5]		161	[7]
Land Construction [Member] | Financing Receivables 30 To 59 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	0	[5]		0	[7]
Land Construction [Member] | Financing Receivables Equal To Greater Than 90 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	12,137	[3],[5]		12,350	[4],[7]
Other Residential Mortgage Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	267,073	[5]		275,424
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Carrying Amount	165,014	[5]		170,766	[7]
Financing Receivable, Current	2,735,919	[5]		2,755,388
Loans held for investment	3,168,006	[5]		3,201,578
90 days past due and still accruing	17,447	[5]		16,017
Other Residential Mortgage Loans [Member] | Financing Receivables 60 To 89 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	87,425	[5]		90,406
Other Residential Mortgage Loans [Member] | Financing Receivables 30 To 59 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	0	[5]		0
Other Residential Mortgage Loans [Member] | Financing Receivables Equal To Greater Than 90 Days Past Due [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Past Due	$ 179,648	[3],[5]		$ 185,018

[1] It is the Corporation's policy to report delinquent residential mortgage loans insured by the FHA or guaranteed by the VA as past-due loans 90 days and still accruing as opposed to non-performing loans since the principal repayment is insured. These balances include $29.6 million of residential mortgage loans insured by the FHA or guaranteed by the VA, which are over 15 months delinquent and are no longer accruing interest as of September 30, 2016.

[2] It is the Corporation's policy to report delinquent residential mortgage loans insured by the FHA or guaranteed by the VA as past-due loans 90 days and still accruing as opposed to non-performing loans since the principal repayment is insured. These balances include $37.3 million of residential mortgage loans insured by the FHA or guaranteed by the VA, which are over 15 months delinquent and are no longer accruing interest as of December 31, 2015.

[3] Includes non-performing loans and accruing loans that are contractually delinquent 90 days or more (i.e., FHA/VA guaranteed loans and credit cards). Credit card loans continue to accrue finance charges and fees until charged-off at 180 days.

[4] Includes non-performing loans and accruing loans that are contractually delinquent 90 days or more (i.e. FHA/VA guaranteed loans and credit cards). Credit card loans continue to accrue finance charges and fees until charged-off at 180 days.

[5] According to the Corporation's delinquency policy and consistent with the instructions for the preparation of the Consolidated Financial Statements for Bank Holding Companies (FR Y-9C) required by the Federal Reserve Board, residential mortgage, commercial mortgage, and construction loans are considered past due when the borrower is in arrears two or more monthly payments. FHA/VA government-guaranteed loans, other residential mortgage loans, commercial mortgage loans, land loans and construction-residential loans past due 30-59 days as of September 30, 2016 amounted to $8.7 million, $144.3 million, $7.6 million, $0.7 million and $0.3 million, respectively.

[6] As of September 30, 2016, includes $45.6 million of defaulted loans collateralizing Government National Mortgage Association ("GNMA") securities for which the Corporation has an unconditional option (but not an obligation) to repurchase the defaulted loans.

[7] According to the Corporation's delinquency policy and consistent with the instructions for the preparation of the Consolidated Financial Statements for Bank Holding Companies (FR Y-9C) required by the Federal Reserve Board, residential mortgage, commercial mortgage, and construction loans are considered past due when the borrower is in arrears two or more monthly payments. FHA/VA government-guaranteed loans, other residential mortgage loans, commercial mortgage loans, land loans and construction-residential loans past due 30-59 days as of December 31, 2015 amounted to $11.0 million, $162.9 million, $38.6 million, $5.7 million and $0.8 million, respectively.

[8] As of December 31, 2015, includes $38.5 million of defaulted loans collateralizing GNMA securities for which the Corporation has an unconditional option (but not an obligation) to repurchase the defaulted loans.