Loans - Impaired Loans (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Financing Receivable, Impaired [Line Items]
Recorded Investment With No Related Allowance	$ 43,527	$ 45,203
Recorded Investment With Related Allowance	172,764	161,531
Total Recorded Investment	216,291	206,734
Unpaid Contractual Principal Balance	254,306	239,964
Related Allowance	28,740	31,013
Commercial real estate loans [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment With No Related Allowance	27,491	33,063
Recorded Investment With Related Allowance	103,140	98,153
Total Recorded Investment	130,631	131,216
Unpaid Contractual Principal Balance	148,911	149,553
Related Allowance	14,632	16,581
Consumer loans [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment With No Related Allowance	1,049	672
Recorded Investment With Related Allowance	137	258
Total Recorded Investment	1,186	930
Unpaid Contractual Principal Balance	1,529	1,169
Related Allowance	11	15
Commercial and industrial [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment With No Related Allowance	3,670	3,236
Recorded Investment With Related Allowance	53,925	46,461
Total Recorded Investment	57,595	49,697
Unpaid Contractual Principal Balance	73,152	62,183
Related Allowance	11,420	12,088
Commercial real estate [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment With No Related Allowance	21,747	26,724
Recorded Investment With Related Allowance	89,450	84,151
Total Recorded Investment	111,197	110,875
Unpaid Contractual Principal Balance	127,316	125,875
Related Allowance	11,729	11,788
Construction [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment With No Related Allowance	5,744	6,339
Recorded Investment With Related Allowance	13,690	14,002
Total Recorded Investment	19,434	20,341
Unpaid Contractual Principal Balance	21,595	23,678
Related Allowance	2,903	4,793
Residential mortgage [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment With No Related Allowance	11,317	8,232
Recorded Investment With Related Allowance	15,562	16,659
Total Recorded Investment	26,879	24,891
Unpaid Contractual Principal Balance	30,714	27,059
Related Allowance	2,677	2,329
Home equity [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment With No Related Allowance	1,049	672
Recorded Investment With Related Allowance	137	258
Total Recorded Investment	1,186	930
Unpaid Contractual Principal Balance	1,529	1,169
Related Allowance	$ 11	$ 15