Purchased Credit Impaired Loans - Accretable Yield or Income Expected to be Collected (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Beginning balance	$ 2,675	$ 3,083	$ 2,890	$ 3,951
Additions		667		667
Accretion	(927)	(1,158)	(1,437)	(4,396)
Reclassification from nonaccretable	675	682	970	3,052
Disposals		(667)		(667)
Ending balance	2,423	$ 2,607	2,423	$ 2,607
Loans acquired with deteriorated credit quality
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, carrying amount	$ 23,300		$ 23,300		$ 25,300