Low-Income Housing Tax Credits (Details) $ in Thousands		3 Months Ended		9 Months Ended		12 Months Ended
		Sep. 30, 2018 USD ($) Fund	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) Fund	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($) Fund
Low-Income Housing Tax Credits [Abstract]
Number of housing equity funds | Fund		4		4		4
Low-income housing investment		$ 3,300		$ 3,300		$ 3,500
Expected affordable housing tax credits				494
Additional committed capital calls expected		248		248		$ 1,100
Tax credits and other tax benefits [Abstract]
Amortization of operating losses		80	$ 77	240	$ 255
Tax benefit of operating losses	[1]	17	26	50	87
Tax credits		137	113	384	346
Total tax benefits		$ 154	$ 139	$ 434	$ 433
Effective income tax rate				21.00%		34.00%

[1] Computed using a 21% tax rate for 2018 and a 34% tax rate for 2017