Securities - Held To Maturity Securities Amortized Cost and Estimated Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Amortized Cost
Due in one year or less	$ 9,247	$ 5,980
Due after one year through five years	81,686	51,936
Due after five years through ten years	50,303	81,300
Due after ten years		0
Total held-to-maturity debt securities	141,236	139,216
Fair Value
Due in one year or less	9,253	5,979
Due after one year through five years	79,931	52,227
Due after five years through ten years	49,048	82,109
Due after ten years		0
Total held-to-maturity debt securities	$ 138,232	$ 140,315