Investment Securities - Schedule of Amortized Cost and Fair Value by Contractual Maturity of Debt Securities (Details) - Municipal securities $ in Thousands	Sep. 30, 2017 USD ($)
Schedule Of Debt Securities [Line Items]
Within 1 year, amortized cost	$ 3,904
1-5 years, amortized cost	12,770
5-10 years, amortized cost	1,489
Amortized Cost	18,163
Within 1 year, fair value	3,911
1-5 years, fair value	12,873
5-10 years, fair value	1,478
Fair Value	$ 18,262
Within 1 year, weighted average yield	1.37%
1-5 years, weighted average yield	2.26%
5-10 years, weighted average yield	4.78%
Weighted Average Yield	2.27%