Commitments and Contingent Liabilities - Narrative (Details)	9 Months Ended
	Sep. 30, 2017 USD ($) derivative_instrument	Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($) derivative_instrument
Loss Contingencies [Line Items]
Notional amount	$ 9,886,000
Best efforts commitments	16,200,000		$ 7,300,000
Fair value of best efforts commitments	82,000		82,000
Hedged interest rate lock commitments	22,300,000		30,600,000
Fair value of hedged interest rate lock commitments	267,000		484,000
Derivative instrument gain (loss)	(265,000)	$ 655,000
Noninterest income realized	777,000	$ 2,500,000
Interest Rate Lock Commitments
Loss Contingencies [Line Items]
Interest rate lock commitments	38,500,000		37,900,000
Forward Contracts | Not Designated as Hedging Instrument
Loss Contingencies [Line Items]
Notional amount	$ 37,000,000		$ 54,300,000
Number of derivative instruments | derivative_instrument	0		0
Fair value of forward contracts	$ 105,000		$ 102,000