Securities - Amortized Cost and Estimated Fair Value of Investment Securities by Contractual Maturity (Detail) $ in Thousands	Sep. 30, 2016 USD ($)
Investments, Debt and Equity Securities [Abstract]
Less than one year, Amortized Cost	$ 16,654
Due after one year through five years, Amortized Cost	49,095
Due after five years through ten years, Amortized Cost	19,025
Due after ten years, Amortized Cost	55,000
Total Amortized Cost	139,774
Less than one year, Estimated Fair Value	16,671
Due after one year through five years, Estimated Fair Value	49,584
Due after five years through ten years, Estimated Fair Value	19,223
Due after ten years, Estimated Fair Value	47,895
Total Estimated Fair Value	$ 133,373