Loans and Leases - Acquired Credit Impaired Loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Receivables [Abstract]
Outstanding principal balance	$ 2,325	$ 8,993
Carrying amount	1,583	7,352
Allowance for loan losses	0	0
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Beginning of period	50	144
Acquisition of credit impaired loans	0	283
Reclassification from nonaccretable discount	891	1,329
Accretable yield amortized to interest income	(926)	(1,672)
Disposals	(4)	(34)
End of period	$ 11	$ 50