Credit Risk Profile Based on Payment Activity (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	$ 5,389,763	$ 4,960,343	$ 4,776,071
Commercial - credit card
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	109,289	95,339
Commercial - credit card | Performing
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	109,289	95,339
Real estate - residential
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	203,953	185,886
Real estate - residential | Performing
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	202,770	184,226
Real estate - residential | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	1,183	1,660
Real estate - HELOC
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	564,480	533,032
Real estate - HELOC | Performing
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	564,196	532,336
Real estate - HELOC | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	284	696
Consumer - credit card
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	323,249	333,646
Consumer - credit card | Performing
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	320,250	329,008
Consumer - credit card | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	2,999	4,638
Consumer - other
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	63,241	94,644
Consumer - other | Performing
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	61,845	93,151
Consumer - other | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	1,396	1,493
Leases
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	18,784	3,834	4,295
Leases | Performing
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	$ 18,784	$ 3,834