Investment Securities - Summary of Maturities of Debt Securities Held to Maturity by Amortized Cost and Estimated Fair Value (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Due in one year or less, Amortized Cost	$ 5,225	$ 7,913
Due after one year through five years, Amortized Cost	216	1,059
Due after five years through ten years, Amortized Cost	0	8,030
Due after ten years, Amortized Cost	1,020	2,997
Amortized Cost	6,461	19,999
Due in one year or less, Estimated Fair Value	5,246	8,005
Due after one year through five years, Estimated Fair Value	217	1,061
Due after five years through ten year, Estimated Fair Value	0	7,134
Due after ten years, Estimated Fair Value	1,020	2,455
Estimated Fair Value, Total	$ 6,483	$ 18,655

Amount of investment in debt security measured at amortized cost (held-to-maturity).

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