Loans - Acquired PCI Loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Receivables [Abstract]
Carrying amount	$ 26,600	$ 37,300
Total outstanding amount	35,300	48,900
Purchase Credit Impaired Loans, Reconciliation of Income Expected to be Collected [Roll Forward]
Beginning balance	4,403	3,797
Increase due to acquired loans	0	92
Accretion of income	(2,950)	(1,883)
Other activity, net	1,552	2,397
Ending balance	$ 3,005	$ 4,403