Loans (Troubled Debt Restructurings) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Modifications [Line Items]
Balance at Restructure	$ 709	$ 8,916	$ 14,833
Balance at Year-end	536	8,339	11,215
Commercial Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Balance at Restructure	709	5,795	6,334
Balance at Year-end	536	5,391	4,937
Commercial and Industrial, Energy [Member]
Financing Receivable, Modifications [Line Items]
Balance at Restructure	0	0	528
Balance at Year-end	0	0	531
Commercial Real Estate, Buildings, Land and Other [Member]
Financing Receivable, Modifications [Line Items]
Balance at Restructure	0	3,121	7,964
Balance at Year-end	0	2,948	5,747
Consumer Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Balance at Restructure	0	0	7
Balance at Year-end	$ 0	$ 0	$ 0