Investment Securities - Summary of Interest Income on Available-For-Sale Investment Securities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Total taxable interest income	$ 1,250	$ 1,067
Total tax-exempt interest income	86	97
Total interest income	1,336	1,164
U.S. Treasury and government sponsored entities
Schedule of Available-for-sale Securities [Line Items]
Total taxable interest income	890	778
Other
Schedule of Available-for-sale Securities [Line Items]
Total taxable interest income	360	289
Municipal securities
Schedule of Available-for-sale Securities [Line Items]
Total tax-exempt interest income	$ 86	$ 97