Number of Loans and Leases Modified in TDRs and Total Recorded Investments and Unpaid Principal Balances (Detail) (Class of Financing Receivable, USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013 Contract	Jun. 30, 2012 Contract	Jun. 30, 2013 Contract	Jun. 30, 2012 Contract
Financing Receivable, Modifications [Line Items]
Number of Loans and Leases	40	33	101	71
Recorded Investment	$ 10.0	$ 28.4	$ 63.0	$ 37.6
Unpaid Principal Balance	13.8	32.0	69.3	43.1
Commercial
Financing Receivable, Modifications [Line Items]
Number of Loans and Leases	3	3	11	9
Recorded Investment	4.7	24.6	5.2	28.5
Unpaid Principal Balance	6.9	27.0	8.0	31.3
Commercial | Commercial and Institutional
Financing Receivable, Modifications [Line Items]
Number of Loans and Leases			7	2
Recorded Investment			0.5	0.6
Unpaid Principal Balance			1.0	1.1
Commercial | Commercial Real Estate Portfolio Segment
Financing Receivable, Modifications [Line Items]
Number of Loans and Leases	3	2	4	6
Recorded Investment	4.7	19.4	4.7	22.7
Unpaid Principal Balance	6.9	21.8	7.0	25.0
Commercial | Lease Financing, Net
Financing Receivable, Modifications [Line Items]
Number of Loans and Leases		1		1
Recorded Investment		5.2		5.2
Unpaid Principal Balance		5.2		5.2
Personal
Financing Receivable, Modifications [Line Items]
Number of Loans and Leases	37	30	90	62
Recorded Investment	5.3	3.8	57.8	9.1
Unpaid Principal Balance	6.9	5.0	61.3	11.8
Personal | Residential Real Estate
Financing Receivable, Modifications [Line Items]
Number of Loans and Leases	36	29	84	61
Recorded Investment	5.3	3.0	45.0	8.3
Unpaid Principal Balance	6.9	4.2	48.5	11.0
Personal | Private Client
Financing Receivable, Modifications [Line Items]
Number of Loans and Leases	1	1	6	1
Recorded Investment		0.8	12.8	0.8
Unpaid Principal Balance		$ 0.8	$ 12.8	$ 0.8