Short-Term Borrowings - Summary of Securities Pledged as Collateral Under Repurchase Agreements (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Offsetting Liabilities [Line Items]
Gross amount of recognized liabilities for repurchase agreements	$ 21,713	$ 25,040
Gross amount of recognized liabilities for repurchase agreements	21,713	25,040
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	840	894
Gross amount of recognized liabilities for repurchase agreements	840	894
Obligations of U.S. Government Agencies [Member]
Offsetting Liabilities [Line Items]
Gross amount of recognized liabilities for repurchase agreements	20,873	24,146
Gross amount of recognized liabilities for repurchase agreements	$ 20,873	$ 24,146