Credit Risk Profile Based on Payment Activity (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	$ 6,759,089	$ 6,520,512	$ 6,010,681
Commercial - credit card [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	121,354	103,270
Commercial - credit card [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	121,329	103,232
Commercial - credit card [Member] | Non-performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	25	38
Real estate - residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	294,405	289,356
Real estate - residential [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	293,459	288,488
Real estate - residential [Member] | Non-performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	946	868
Real estate - Home Equity Line of Credit [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	570,429	566,128
Real estate - Home Equity Line of Credit [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	570,104	565,918
Real estate - Home Equity Line of Credit [Member] | Non-performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	325	210
Consumer - credit card [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	300,296	318,336
Consumer - credit card [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	299,427	317,305
Consumer - credit card [Member] | Non-performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	869	1,031
Consumer - other [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	61,693	62,912
Consumer - other [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	61,341	62,542
Consumer - other [Member] | Non-performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	352	370
Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	24,053	23,981	19,901
Leases [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity	24,053	23,981
Leases [Member] | Non-performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit Risk Profile Based on Payment Activity