Securities - Amortized Cost and Fair Value of Available-for-Sale Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 685,170
Debt Securities, Available-for-sale, Fair Value	680,056	$ 693,147
Obligations of the U.S. Treasury, U.S. government corporations and agencies, and obligations of states and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Due in one year or less, amortized cost	11,137
Due after one year through five years, amortized cost	157,986
Due after five years through ten years, amortized cost	61,489
Due after ten years, amortized cost	28,485
Debt securities available-for-sale, maturity, amortized cost	259,097
Due in one year or less, fair value	11,155
Due after one year through five years, fair value	157,921
Due after five years through ten years, fair value	62,017
Due after ten years, fair value	29,170
Debt securities available-for-sale, maturity, fair value	260,263
Collateralized mortgage obligations of U.S. government corporations and agencies
Debt Securities, Available-for-sale [Line Items]
Debt securities available-for-sale with maturities, amortized cost	149,849
Debt securities available-for-sale with maturities, fair value Fair Value	148,659
Debt Securities, Available-for-sale, Amortized Cost	149,849	109,916
Debt Securities, Available-for-sale, Fair Value	148,659	108,688
Residential mortgage-backed securities of U.S. government corporations and agencies
Debt Securities, Available-for-sale [Line Items]
Debt securities available-for-sale with maturities, amortized cost	24,564
Debt securities available-for-sale with maturities, fair value Fair Value	24,350
Debt Securities, Available-for-sale, Amortized Cost	24,564	32,388
Debt Securities, Available-for-sale, Fair Value	24,350	32,854
Commercial mortgage-backed securities of U.S. government corporations and agencies
Debt Securities, Available-for-sale [Line Items]
Debt securities available-for-sale with maturities, amortized cost	251,660
Debt securities available-for-sale with maturities, fair value Fair Value	246,784
Debt Securities, Available-for-sale, Amortized Cost	251,660	244,018	[1]
Debt Securities, Available-for-sale, Fair Value	$ 246,784	$ 242,221	[1]

[1] Includes a $5.9 million security purchase that was pending settlement as of December 31, 2017.