Investment Securities - Schedule of Investments Classified by Contractual Maturity Date (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Amortized cost, Due in less than one year	$ 34,943
Amortized cost, Due after one year but within five years	177,050
Amortized cost, Due after five years but within ten years	103,823
Amortized cost, Due after ten years	77,815
Amortized cost, Total	393,631	$ 388,520
Estimated fair value, Due in less than one year	34,847
Estimated fair value, Due after one year but within five years	174,149
Estimated fair value, Due after five years but within ten years	102,522
Estimated fair value, Due after ten years	76,827
Estimated fair value, Total	$ 388,345	$ 387,983