Loans - Average Recorded Investment In Impaired Loans (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	$ 51,945	$ 73,476	$ 48,649	$ 77,559
Commercial and industrial, Energy [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	581	269	555	402
Commercial and industrial, Other commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	31,088	33,613	25,977	38,032
Commercial real estate, Buildings, land and other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	19,198	37,960	20,998	37,149
Commercial real estate, Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	295	508	226	793
Consumer Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	657	788	694	818
Consumer and Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	$ 126	$ 338	$ 199	$ 365