Loans - Average Recorded Investment In Impaired Loans (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	$ 47,514	$ 80,032	$ 47,828	$ 80,153
Commercial and industrial, Energy [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	526	0	527	356
Commercial and industrial, Other commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	25,259	40,331	24,286	40,489
Commercial real estate, Buildings, land and other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	20,460	37,473	21,829	37,035
Commercial real estate, Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	307	1,035	204	1,057
Consumer Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	704	818	717	833
Consumer and Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	$ 258	$ 375	$ 265	$ 383