Covered loans in non-performing status and accruing loans past-due 90 days or more by loan class (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013		Dec. 31, 2012
Commercial Real Estate Construction Financing Receivable Member
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual loans	$ 0		$ 78,140
Mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual loans	6,423		53
Covered Under Loss Sharing Agreements With F D I C [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual loans	25,769	[1]	74,410	[1]
Financing Receivable Recorded Investment 90 Days Past Due And Still Accruing	414	[1]	769	[1]
Covered Under Loss Sharing Agreements With F D I C [Member] | Commercial Real Estate Portfolio Segment Member
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual loans	7,202		14,628
Financing Receivable Recorded Investment 90 Days Past Due And Still Accruing	0		0
Covered Under Loss Sharing Agreements With F D I C [Member] | Commercial And Industrial Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual loans	10,963		48,743
Financing Receivable Recorded Investment 90 Days Past Due And Still Accruing	223		504
Covered Under Loss Sharing Agreements With F D I C [Member] | Commercial Real Estate Construction Financing Receivable Member
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual loans	5,696		8,363
Financing Receivable Recorded Investment 90 Days Past Due And Still Accruing	0		0
Covered Under Loss Sharing Agreements With F D I C [Member] | Mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual loans	1,575		2,133
Financing Receivable Recorded Investment 90 Days Past Due And Still Accruing	0		0
Covered Under Loss Sharing Agreements With F D I C [Member] | Consumer Portfolio Segment Member
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual loans	333		543
Financing Receivable Recorded Investment 90 Days Past Due And Still Accruing	$ 191		$ 265

[1] Covered loans accounted for under ASC Subtopic 310-30 are excluded from the above table as they are considered to be performing due to the application of the accretion method, in which these loans will accrete interest income over the remaining life of the loans using estimated cash flow analyses.