LOAN PORTFOLIO - Corporation's Aging of Loans Held for Investment Portfolio (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014		Mar. 31, 2014
Accounts Notes And Loans Receivable [Line Items]
30-59 Days Past Due	$ 120,984		$ 118,154
60-89 Days, Past Due	128,454		139,659
90 days or more, Past Due	725,665	[1]	671,122	[2]
Total Past Due	975,103		928,935
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Carrying Amount Net	181,114		102,604
Financing Receivable, Current	8,329,155		8,230,897
Loans held for investment	9,485,372		9,262,436		9,566,785
90 days past due and still accruing	162,121	[3]	147,226	[4]
Fha Va And Other Government Guaranteed Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
30-59 Days Past Due	0	[3],[5],[6]	0	[4],[7]
60-89 Days, Past Due	8,200	[3],[5],[6]	9,733	[4],[7]
90 days or more, Past Due	96,086	[1],[3],[5],[6]	81,055	[4],[7]
Total Past Due	104,286	[3],[5],[6]	90,788	[4],[7]
Financing Receivable, Current	51,376	[3],[5],[6]	62,782	[4],[7]
Loans held for investment	155,662	[3],[5],[6]	153,570	[4],[7]
90 days past due and still accruing	96,086	[3],[5],[6]	81,055	[4],[7]
Residential Mortgage [Member]
Accounts Notes And Loans Receivable [Line Items]
30-59 Days Past Due	0	[5]	0	[8]
60-89 Days, Past Due	88,209	[5]	78,336	[8]
90 days or more, Past Due	191,014	[1],[5]	199,078	[2],[8]
Total Past Due	279,223	[5]	277,414	[8]
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Carrying Amount Net	177,601	[5]	98,494	[8]
Financing Receivable, Current	2,719,134	[5]	2,481,709	[8]
Loans held for investment	3,175,958	[5]	2,857,617	[8]
90 days past due and still accruing	18,431	[3],[5]	18,371	[4],[8]
Commercial And Industrial [Member]
Accounts Notes And Loans Receivable [Line Items]
30-59 Days Past Due	22,933		22,217
60-89 Days, Past Due	3,193		7,445
90 days or more, Past Due	207,063	[1]	143,928	[2]
Total Past Due	233,189		173,590
Financing Receivable, Current	2,209,678		2,305,847
Loans held for investment	2,442,867		2,479,437
90 days past due and still accruing	20,563	[3]	21,381	[4]
Commercial Mortgage Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
30-59 Days Past Due	0	[5]	0	[8]
60-89 Days, Past Due	1,564	[5]	15,482	[8]
90 days or more, Past Due	165,778	[1],[5]	171,281	[2],[8]
Total Past Due	167,342	[5]	186,763	[8]
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Carrying Amount Net	3,279	[5]	3,393	[8]
Financing Receivable, Current	1,478,642	[5]	1,475,631	[8]
Loans held for investment	1,649,263	[5]	1,665,787	[8]
90 days past due and still accruing	23,393	[3],[5]	22,808	[4],[8]
Auto loans [Member]
Accounts Notes And Loans Receivable [Line Items]
30-59 Days Past Due	76,721		77,385
60-89 Days, Past Due	18,548		19,665
90 days or more, Past Due	19,043	[1]	22,276	[2]
Total Past Due	114,312		119,326
Financing Receivable, Current	914,058		941,456
Loans held for investment	1,028,370		1,060,782
90 days past due and still accruing	0	[3]	0	[4]
Finance Leases [Member]
Accounts Notes And Loans Receivable [Line Items]
30-59 Days Past Due	10,975		8,751
60-89 Days, Past Due	2,893		2,734
90 days or more, Past Due	2,979	[1]	5,245	[2]
Total Past Due	16,847		16,730
Financing Receivable, Current	213,336		215,396
Loans held for investment	230,183		232,126
90 days past due and still accruing	0	[3]	0	[4]
Consumer Loan [Member]
Accounts Notes And Loans Receivable [Line Items]
30-59 Days Past Due	10,355		9,801
60-89 Days, Past Due	5,464		6,054
90 days or more, Past Due	16,339	[1]	18,671	[2]
Total Past Due	32,158		34,526
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Carrying Amount Net	234		717
Financing Receivable, Current	646,237		654,394
Loans held for investment	678,629		689,637
90 days past due and still accruing	3,448	[3]	3,377	[4]
Commercial Construction [Member]
Accounts Notes And Loans Receivable [Line Items]
30-59 Days Past Due	0		0
60-89 Days, Past Due	0		0
90 days or more, Past Due	0	[1]	0	[2]
Total Past Due	0		0
Financing Receivable, Current	27,456		24,562
Loans held for investment	27,456		24,562
90 days past due and still accruing	0	[3]	0	[4]
Residential Construction [Member]
Accounts Notes And Loans Receivable [Line Items]
30-59 Days Past Due	0	[5]	0	[8]
60-89 Days, Past Due	0	[5]	0	[8]
90 days or more, Past Due	13,072	[1],[5]	14,324	[2],[8]
Total Past Due	13,072	[5]	14,324	[8]
Financing Receivable, Current	29,722	[5]	28,673	[8]
Loans held for investment	42,794	[5]	42,997	[8]
90 days past due and still accruing	0	[3],[5]	0	[4],[8]
Land Construction [Member]
Accounts Notes And Loans Receivable [Line Items]
30-59 Days Past Due	0	[5]	0	[8]
60-89 Days, Past Due	383	[5]	210	[8]
90 days or more, Past Due	14,291	[1],[5]	15,264	[2],[8]
Total Past Due	14,674	[5]	15,474	[8]
Financing Receivable, Current	39,516	[5]	40,447	[8]
Loans held for investment	54,190	[5]	55,921	[8]
90 days past due and still accruing	$ 200	[3],[5]	$ 234	[4],[8]

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

[2] Includes non-performing loans and accruing loans which 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.

[3] 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 $30.1 million of residential mortgage loans insured by the FHA or guaranteed by the VA, which are over 18 months delinquent, and are no longer accruing interest as of March 31, 2015.

[4] 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 $40.4 million of residential mortgage loans insured by the FHA or guaranteed by the VA, which are over 18 months delinquent, and are no longer accruing interest as of December 31, 2014.

[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 March 31, 2015 amounted to $12.2 million, $177.4 million, $38.4 million, $6.1 million, and $1.6 million, respectively.

[6] As of March 31, 2015, includes $26.2 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] As of December 31, 2014, includes $9.3 million of defaulted loans collateralizing GNMA securities for which the Corporation has an unconditional option (but not an obligation) to repurchase the defaulted loans.

[8] 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, 2014 amounted to $14.0 million, $189.1 million, $20.8 million, $0.8 million and $1.0 million , respectively.