Employee Stock Ownership Plan - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Retirement Benefits [Abstract]
ESOP, Number of shares committed to be released annually (shares)	75,912
Fair Value of unallocated shares	$ 40,800		$ 39,700
ESOP expense	$ 378	$ 341