Number of Loans and Leases Modified in TDRs and Total Recorded Investments and Unpaid Principal Balances (Detail) (Class of Financing Receivable, USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014 Contract	Jun. 30, 2013 Contract	Jun. 30, 2014 Contract	Jun. 30, 2013 Contract
Financing Receivable, Modifications [Line Items]
Number of Loans and Leases	38	40	74	101
Recorded Investment	$ 5,900,000	$ 10,000,000	$ 10,100,000	$ 63,000,000
Unpaid Principal Balance	7,000,000	13,800,000	11,400,000	69,300,000
Commercial
Financing Receivable, Modifications [Line Items]
Number of Loans and Leases	2	3	3	11
Recorded Investment	700,000	4,700,000	1,400,000	5,200,000
Unpaid Principal Balance	1,000,000	6,900,000	1,700,000	8,000,000
Commercial | Commercial and Institutional
Financing Receivable, Modifications [Line Items]
Number of Loans and Leases	2		2	7
Recorded Investment	700,000		700,000	500,000
Unpaid Principal Balance	1,000,000		1,000,000	1,000,000
Commercial | Commercial Real Estate Portfolio Segment
Financing Receivable, Modifications [Line Items]
Number of Loans and Leases		3	1	4
Recorded Investment		4,700,000	700,000	4,700,000
Unpaid Principal Balance		6,900,000	700,000	7,000,000
Personal
Financing Receivable, Modifications [Line Items]
Number of Loans and Leases	36	37	71	90
Recorded Investment	5,200,000	5,300,000	8,700,000	57,800,000
Unpaid Principal Balance	6,000,000	6,900,000	9,700,000	61,300,000
Personal | Residential Real Estate
Financing Receivable, Modifications [Line Items]
Number of Loans and Leases	34	36	68	84
Recorded Investment	4,900,000	5,300,000	8,400,000	45,000,000
Unpaid Principal Balance	5,700,000	6,900,000	9,400,000	48,500,000
Personal | Private Client
Financing Receivable, Modifications [Line Items]
Number of Loans and Leases	2	1	3	6
Recorded Investment	300,000		300,000	12,800,000
Unpaid Principal Balance	$ 300,000		$ 300,000	$ 12,800,000