Loans - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment, Past Due [Line Items]
Reduction in interest income	$ 700,000	$ 700,000	$ 600,000
Loans and Leases Receivable, Related Parties	1,100,000	2,100,000
Loans and Leases Receivable, Related Parties, Additions	0
Loans Pledged as Collateral	211,000,000	415,000,000
Troubled Debt Restructuring Outstanding	15,600,000	17,700,000
Impaired Financing Receivable, Average Recorded Investment	30,900,000	31,200,000	38,500,000
Loans and Leases Receivable, Impaired, Troubled Debt, Interest Income	1,500,000	1,600,000	900,000
Loans and Leases Receivable, Impaired, Interest Income Recognized, Change in Present Value Attributable to Passage of Time	300,000	200,000	$ 200,000
Commercial and Financial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Operating Lease, Liability	30,300,000	0
PCI Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Deferred Costs, Noncurrent	$ 11,500,000	$ 10,600,000