Allowance For Loan Losses and Credit Quality Information (Analysis Of Impaired Loans) (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended		12 Months Ended
	Sep. 30, 2012		Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Ending Loan Balances	$ 50,164		$ 79,979
Loans with No Specific Reserve	42,301	[1]	58,106	[1]
Loans with Specific Reserve	7,863		21,873
Related Specific Reserve	2,873		4,713
Contractual Principal Balances	83,729		105,055
Average Loan Balances	85,903		87,352
Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Ending Loan Balances	3,579		23,193
Loans with No Specific Reserve	1,735	[1]	19,353	[1]
Loans with Specific Reserve	1,844		3,840
Related Specific Reserve	1,244		2,630
Contractual Principal Balances	10,714		26,815
Average Loan Balances	8,530		22,396
Commercial Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Ending Loan Balances	5,875		15,814
Loans with No Specific Reserve	5,243	[1]	13,602	[1]
Loans with Specific Reserve	632		2,212
Related Specific Reserve	90		295
Contractual Principal Balances	9,316		21,278
Average Loan Balances	15,394		16,237
Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Ending Loan Balances	2,620		22,124
Loans with No Specific Reserve	2,121	[1]	14,166	[1]
Loans with Specific Reserve	499		7,958
Related Specific Reserve	94		723
Contractual Principal Balances	19,245		34,862
Average Loan Balances	25,446		27,323
Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Ending Loan Balances	18,072		16,227
Loans with No Specific Reserve	15,126	[1]	9,649	[1]
Loans with Specific Reserve	2,946		6,578
Related Specific Reserve	1,199		964
Contractual Principal Balances	19,919		19,312
Average Loan Balances	18,502		17,480
Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Ending Loan Balances	6,694		2,621
Loans with No Specific Reserve	5,988	[1]	1,336	[1]
Loans with Specific Reserve	706		1,285
Related Specific Reserve	24		101
Contractual Principal Balances	8,242		2,788
Average Loan Balances	4,113		3,916
Owner Occupied Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Ending Loan Balances	13,324	[2]
Loans with No Specific Reserve	12,088	[1],[2]
Loans with Specific Reserve	1,236	[2]
Related Specific Reserve	222	[2]
Contractual Principal Balances	16,293	[2]
Average Loan Balances	$ 13,918	[2]

[1] Reflects loan balances at their remaining book balance.

[2] Prior to 2012, owner-occupied commercial loans were included in commercial loan balances.