Loans - Impaired Loans (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Financing Receivable, Impaired [Line Items]
Recorded Investment With No Related Allowance	$ 45,203	$ 38,185
Recorded Investment With Related Allowance	161,531	145,890
Total Recorded Investment	206,734	184,075
Unpaid Contractual Principal Balance	239,964	212,899
Related Allowance	31,013	23,243
Commercial real estate loans [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment With No Related Allowance	33,063	30,994
Recorded Investment With Related Allowance	98,153	76,976
Total Recorded Investment	131,216	107,970
Unpaid Contractual Principal Balance	149,553	119,514
Related Allowance	16,581	8,516
Consumer loans [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment With No Related Allowance	672
Recorded Investment With Related Allowance	258	242
Total Recorded Investment	930	242
Unpaid Contractual Principal Balance	1,169	242
Related Allowance	15	45
Commercial and industrial [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment With No Related Allowance	3,236	6,193
Recorded Investment With Related Allowance	46,461	48,665
Total Recorded Investment	49,697	54,858
Unpaid Contractual Principal Balance	62,183	71,111
Related Allowance	12,088	11,105
Commercial real estate [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment With No Related Allowance	26,724	26,741
Recorded Investment With Related Allowance	84,151	56,978
Total Recorded Investment	110,875	83,719
Unpaid Contractual Principal Balance	125,875	91,448
Related Allowance	11,788	7,108
Construction [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment With No Related Allowance	6,339	4,253
Recorded Investment With Related Allowance	14,002	19,998
Total Recorded Investment	20,341	24,251
Unpaid Contractual Principal Balance	23,678	28,066
Related Allowance	4,793	1,408
Residential mortgage [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment With No Related Allowance	8,232	998
Recorded Investment With Related Allowance	16,659	20,007
Total Recorded Investment	24,891	21,005
Unpaid Contractual Principal Balance	27,059	22,032
Related Allowance	2,329	3,577
Home equity [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment With No Related Allowance	672
Recorded Investment With Related Allowance	258	242
Total Recorded Investment	930	242
Unpaid Contractual Principal Balance	1,169	242
Related Allowance	$ 15	$ 45