Investments in Qualified Affordable Housing Projects - Components of Qualified Affordable Housing Projects Included in Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Equity Method Investments and Joint Ventures [Abstract]
Tax credit amortization	$ 472	$ 353	$ 995	$ 1,001
Tax credits and other benefits	(671)	(503)	(1,519)	(1,445)
Total	$ (199)	$ (150)	$ (524)	$ (444)