Low-Income Housing Tax Credits (Details) $ in Thousands		3 Months Ended		6 Months Ended		12 Months Ended
		Jun. 30, 2018 USD ($) Fund	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) Fund	Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($) Fund
Low-Income Housing Tax Credits [Abstract]
Number of housing equity funds | Fund		4		4		4
Low-income housing investment		$ 3,400		$ 3,400		$ 3,500
Expected affordable housing tax credits				495
Additional committed capital calls expected		1,100		1,100		$ 1,100
Tax credits and other tax benefits [Abstract]
Amortization of operating losses		80	$ 98	160	$ 178
Tax benefit of operating losses	[1]	17	33	34	61
Tax credits		123	138	247	233
Total tax benefits		$ 140	$ 171	$ 281	$ 294
Effective income tax rate				21.00%		34.00%

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