Investment in Qualified Affordable Housing Investment in Qualified Affordable Housing (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Amortization Method Qualified Affordable Housing Project Investments, Amortization	$ 1,851	$ 1,864
Affordable housing tax credit investments	47,818		$ 49,669
Affordable Housing Program Obligation	14,282		$ 14,282
Affordable Housing Tax Credits and Other Tax Benefits, Amount	$ 2,700	$ 2,400