Low-Income Housing Tax Credits (Details) $ in Thousands		3 Months Ended
		Mar. 31, 2018 USD ($) Fund	Mar. 31, 2017 USD ($)	Dec. 31, 2017 USD ($) Fund
Low-Income Housing Tax Credits [Abstract]
Number of housing equity funds | Fund		4		4
Low-income housing investment		$ 3,600		$ 3,500
Expected affordable housing tax credits		442
Additional committed capital calls expected		1,100		$ 1,100
Impairment loss on investments		0	$ 0
Tax credits and other tax benefits [Abstract]
Amortization of operating losses		80	80
Tax benefit of operating losses	[1]	17	27
Tax credits		124	95
Total tax benefits		$ 141	$ 122
Effective income tax rate		21.00%	34.00%

[1] Computed using a 21% tax rate for the first three months of 2018 and a 34% tax rate for the first three months of 2017.