LOAN PORTFOLIO - Corporation's Credit Quality Indicators by Loan (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014		Dec. 31, 2013
Financing Receivable Recorded Investment [Line Items]
Commercial mortgage loans	$ 1,812,094		$ 1,823,608
Construction loans	141,689		168,713
Commercial and Industrial loans	2,515,384		3,028,322
Land	57,775		80,373
Residential Construction [Member]
Financing Receivable Recorded Investment [Line Items]
Construction loans	67,584		71,509
Commercial Construction [Member]
Financing Receivable Recorded Investment [Line Items]
Construction loans	16,330		16,831
Substandard [Member]
Financing Receivable Recorded Investment [Line Items]
Commercial mortgage loans	294,134		317,365
Commercial and Industrial loans	225,941		205,807
Land	17,648		31,777
Substandard [Member] | Residential Construction [Member]
Financing Receivable Recorded Investment [Line Items]
Construction loans	13,072		27,829
Substandard [Member] | Commercial Construction [Member]
Financing Receivable Recorded Investment [Line Items]
Construction loans	11,790		16,022
Doubtful [Member]
Financing Receivable Recorded Investment [Line Items]
Commercial mortgage loans	1,710		9,160
Commercial and Industrial loans	5,515		7,998
Land	0		3,308
Doubtful [Member] | Residential Construction [Member]
Financing Receivable Recorded Investment [Line Items]
Construction loans	777		2,209
Doubtful [Member] | Commercial Construction [Member]
Financing Receivable Recorded Investment [Line Items]
Construction loans	0		0
Unlikely To Be Collected Financing Receivable [Member]
Financing Receivable Recorded Investment [Line Items]
Commercial mortgage loans	0		234
Commercial and Industrial loans	794		973
Land	0		52
Unlikely To Be Collected Financing Receivable [Member] | Residential Construction [Member]
Financing Receivable Recorded Investment [Line Items]
Construction loans	0		241
Unlikely To Be Collected Financing Receivable [Member] | Commercial Construction [Member]
Financing Receivable Recorded Investment [Line Items]
Construction loans	0		0
Total Adversely Classified [Member]
Financing Receivable Recorded Investment [Line Items]
Commercial mortgage loans	295,844	[1]	326,759	[1]
Commercial and Industrial loans	232,250	[1]	214,778	[1]
Land	17,648	[1]	35,137	[1]
Total Adversely Classified [Member] | Residential Construction [Member]
Financing Receivable Recorded Investment [Line Items]
Construction loans	13,849	[1]	30,279	[1]
Total Adversely Classified [Member] | Commercial Construction [Member]
Financing Receivable Recorded Investment [Line Items]
Construction loans	$ 11,790	[1]	$ 16,022	[1]

[1] Excludes $54.6 million ($7.8 million land, $39.1 million construction-commercial, $0.9 million construction-residential and $6.8 million commercial mortgage) and $54.8 million ($7.8 million land, $39.1 million construction-commercial, $0.9 million construction-residential and $7.0 million commercial mortgage) as of September 30, 2014 and December 31, 2013, respectively, of non-performing loans held for sale.