Loans - Outstanding Principal and Carrying Amount of Acquired Loans (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Outstanding principal balance and the carrying amount of loan acquired [Abstract]
Outstanding principal balance	$ 66,544	$ 79,523
Carrying amount	61,537	73,796
Outstanding principal balance and the carrying amount of loan acquired, impaired [Abstract]
Outstanding principal balance	25,285	27,876
Carrying amount	$ 21,221	$ 23,430