Derivative Instruments and Hedging Activities - Fair Value Hedges (Details) - Fair Value Hedging $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gross notional amount outstanding	$ 5,458
Derivative liability fair value in other liabilities	$ (101)
Weighted-average interest rate received	3.38%
Weighted-average interest rate paid	5.96%
Weighted-average maturity (in years)	10 months 4 days
Fair value of derivative	$ 110	[1]

[1] This amount represents the fair value if credit risk related contingent features were triggered.