Loans - Average Recorded Investment In Impaired Loans (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	$ 73,476	$ 89,897	$ 77,559	$ 88,127
Commercial and industrial, Energy [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	269	0	402	0
Commercial and industrial, Other commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	33,613	44,140	38,032	43,087
Commercial real estate, Buildings, land and other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	37,960	42,569	37,149	41,283
Commercial real estate, Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	508	1,671	793	1,465
Consumer Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	788	1,087	818	1,805
Consumer and Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	$ 338	$ 430	$ 365	$ 487