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Securities Held-to-Maturity - Schedule of Securities Held-to-Maturity (Detail) - USD ($)
$ in Thousands
Mar. 31, 2017
Dec. 31, 2016
Schedule of Held-to-maturity Securities [Line Items]    
Federal agency debt instruments (amortized cost) $ 23,202 $ 22,496
Federal Agency [Member]    
Schedule of Held-to-maturity Securities [Line Items]    
Federal agency debt instruments (amortized cost) $ 23,202 $ 22,496