Short-Term Borrowings - Summary of Securities Pledged as Collateral Under Repurchase Agreements (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Offsetting Liabilities [Line Items]
Gross amount of recognized liabilities for repurchase agreements	$ 17,460	$ 21,613
Gross amount of recognized liabilities for repurchase agreements	17,460	21,613
Amounts related to agreements not included in offsetting disclosures above	0	0
U.S.Treasury Securities [Member]
Offsetting Liabilities [Line Items]
Gross amount of recognized liabilities for repurchase agreements	744	876
Gross amount of recognized liabilities for repurchase agreements	744	876
Obligations of U.S. Government Agencies [Member]
Offsetting Liabilities [Line Items]
Gross amount of recognized liabilities for repurchase agreements	16,716	20,737
Gross amount of recognized liabilities for repurchase agreements	$ 16,716	$ 20,737