Derivatives - Narrative (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2018 USD ($) derivative_swap	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) derivative_swap	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Derivatives, Fair Value [Line Items]
Collateral requirement threshold			$ 250,000
Collateral posted	$ 300,000		300,000		$ 300,000
Derivative notional amount	$ 15,200,000		$ 15,200,000		12,500,000
Number of derivatives | derivative_swap	4		4
Derivative fee income	$ 70,000	$ 10,000	$ 70,000	$ 26,000
Residential Mortgage Holding Company
Derivatives, Fair Value [Line Items]
Commitments to originate mortgage loans held for sale	69,000,000		69,000,000		$ 43,600,000
Variable to Fixed
Derivatives, Fair Value [Line Items]
Derivative notional amount	$ 7,600,000		$ 7,600,000
Number of derivatives | derivative_swap	2		2
Fixed to Variable
Derivatives, Fair Value [Line Items]
Derivative notional amount	$ 7,600,000		$ 7,600,000
Number of derivatives | derivative_swap	2		2
Subordinated Debt
Derivatives, Fair Value [Line Items]
Junior subordinated debenture		$ 10,000,000.0		$ 10,000,000.0
Junior subordinated debenture, effective interest rate		3.72%		3.72%
Debt instrument, interest rate during period	3.70%
Subordinated Debt | LIBOR
Derivatives, Fair Value [Line Items]
Debt instrument, basis spread on variable rate		1.37%
Designated as Hedging Instrument | Interest rate swaps
Derivatives, Fair Value [Line Items]
Cash pledged to collateralize fair value exposure on interest rate swap	$ 400,000		$ 400,000
Unrealized gain on interest rate swap	$ 1,000,000		$ 1,000,000