Loans - Loans by Class Modified as Troubled Debt Restructurings (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended	3 Months Ended		12 Months Ended	3 Months Ended		12 Months Ended	3 Months Ended		12 Months Ended	3 Months Ended		12 Months Ended	3 Months Ended		12 Months Ended	3 Months Ended
	Mar. 31, 2014 Loans	Dec. 31, 2013 Loans	Mar. 31, 2013 Trouble Debt Restructuring [Member] Loans	Mar. 31, 2014 Commercial, Industrial, and Agricultural [Member] Loans	Dec. 31, 2013 Commercial, Industrial, and Agricultural [Member] Loans	Mar. 31, 2013 Commercial, Industrial, and Agricultural [Member] Trouble Debt Restructuring [Member] Loans	Mar. 31, 2014 Commercial Mortgages [Member] Loans	Dec. 31, 2013 Commercial Mortgages [Member] Loans	Mar. 31, 2013 Commercial Mortgages [Member] Trouble Debt Restructuring [Member] Loans	Mar. 31, 2014 Residential Real Estate [Member] Loans	Dec. 31, 2013 Residential Real Estate [Member] Loans	Mar. 31, 2013 Residential Real Estate [Member] Trouble Debt Restructuring [Member] Loans	Mar. 31, 2014 Consumer [Member] Loans	Dec. 31, 2013 Consumer [Member] Loans	Mar. 31, 2013 Consumer [Member] Trouble Debt Restructuring [Member] Loans	Mar. 31, 2014 Credit Cards [Member] Loans	Dec. 31, 2013 Credit Cards [Member] Loans	Mar. 31, 2013 Credit Cards [Member] Trouble Debt Restructuring [Member] Loans
Financing Receivable, Modifications [Line Items]
Number of Loans	12	12	1	5	5	0	7	7	1	0	0	0	0	0	0	0	0	0
Pre-Modification Outstanding Recorded Investment			$ 346			$ 0			$ 346			$ 0			$ 0			$ 0
Post-Modification Outstanding Recorded Investment			$ 403			$ 0			$ 403			$ 0			$ 0			$ 0