Summary of Loan Classes and Aging of Past Due Loans (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due and Accruing	$ 15,862	$ 13,360
Greater than 90 Days Past Due and Accruing	5,101	3,218
Non- Accrual Loans	30,153	30,706
Total Past Due	51,116	47,284
Current	6,707,973	6,473,228
Total Loans	6,759,089	6,520,512	6,010,681
Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due and Accruing	3,478	2,107
Greater than 90 Days Past Due and Accruing	2,023	135
Non- Accrual Loans	8,611	8,042
Total Past Due	14,112	10,284
Current	3,475,917	3,291,219
Total Loans	3,490,029	3,301,503
Commercial - credit card [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due and Accruing	368	362
Greater than 90 Days Past Due and Accruing	126	82
Non- Accrual Loans	25	38
Total Past Due	519	482
Current	120,835	102,788
Total Loans	121,354	103,270
Real estate - construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due and Accruing	768	186
Greater than 90 Days Past Due and Accruing
Non- Accrual Loans	921	934
Total Past Due	1,689	1,120
Current	184,271	151,755
Total Loans	185,960	152,875
Real estate - commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due and Accruing	2,660	3,611
Greater than 90 Days Past Due and Accruing		344
Non- Accrual Loans	18,104	19,213
Total Past Due	20,764	23,168
Current	1,690,106	1,678,983
Total Loans	1,710,870	1,702,151
Real estate - residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due and Accruing	1,114	1,257
Greater than 90 Days Past Due and Accruing		13
Non- Accrual Loans	946	868
Total Past Due	2,060	2,138
Current	292,345	287,218
Total Loans	294,405	289,356
Real estate - Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due and Accruing	1,983	880
Greater than 90 Days Past Due and Accruing		6
Non- Accrual Loans	325	210
Total Past Due	2,308	1,096
Current	568,121	565,032
Total Loans	570,429	566,128
Consumer - credit card [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due and Accruing	2,391	3,230
Greater than 90 Days Past Due and Accruing	2,853	2,448
Non- Accrual Loans	869	1,031
Total Past Due	6,113	6,709
Current	294,183	311,627
Total Loans	300,296	318,336
Consumer - other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due and Accruing	2,943	1,727
Greater than 90 Days Past Due and Accruing	99	190
Non- Accrual Loans	352	370
Total Past Due	3,394	2,287
Current	58,299	60,625
Total Loans	61,693	62,912
Leases [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due and Accruing	157
Greater than 90 Days Past Due and Accruing
Non- Accrual Loans
Total Past Due	157
Current	23,896	23,981
Total Loans	$ 24,053	$ 23,981	$ 19,901