Low-Income Housing Tax Credits (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2017 USD ($) Fund	Mar. 31, 2016 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($) Fund
Low-Income Housing Tax Credits [Abstract]
Affordable Housing Program, Number of Investments | Fund	4			4
Amortization Method Qualified Affordable Housing Project Investments	$ 3,805			$ 3,885
Qualified Affordable Housing Project Investments, Commitment	2,542			$ 2,542
Affordable Housing Investment Commitments, Term Expiration Year			2032
Expected Affordable Housing Tax Credits, Amount			$ 471
Affordable Housing Tax Credits and Other Tax Benefits, Amount	$ 122	$ 126