Loans and Credit Quality - Newly Restructured Loans by Concession (Details)	3 Months Ended
	Mar. 31, 2018 USD ($) contract
Financing Receivable, Modifications [Line Items]
Pre-modification, number of contracts | contract	6
Pre-modification, total modification	$ 4,398,000
Post-modification, number of contracts | contract	6
Post-modification, total modification	$ 3,432,000
Commercial | AQR Substandard
Financing Receivable, Modifications [Line Items]
Pre-modification, number of contracts | contract	4
Pre-modification, total modification	$ 2,704,000
Post-modification, number of contracts | contract	4
Post-modification, total modification	$ 1,738,000
Real estate term owner occupied | AQR Substandard
Financing Receivable, Modifications [Line Items]
Pre-modification, number of contracts | contract	2
Pre-modification, total modification	$ 1,694,000
Post-modification, number of contracts | contract	2
Post-modification, total modification	$ 1,694,000
Rate Modification
Financing Receivable, Modifications [Line Items]
Pre-modification, total modification	0
Post-modification, total modification	0
Rate Modification | Commercial | AQR Substandard
Financing Receivable, Modifications [Line Items]
Pre-modification, total modification	0
Post-modification, total modification	0
Rate Modification | Real estate term owner occupied | AQR Substandard
Financing Receivable, Modifications [Line Items]
Pre-modification, total modification	0
Post-modification, total modification	0
Term Modification
Financing Receivable, Modifications [Line Items]
Pre-modification, total modification	0
Post-modification, total modification	0
Term Modification | Commercial | AQR Substandard
Financing Receivable, Modifications [Line Items]
Pre-modification, total modification	0
Post-modification, total modification	0
Term Modification | Real estate term owner occupied | AQR Substandard
Financing Receivable, Modifications [Line Items]
Pre-modification, total modification	0
Post-modification, total modification	0
Payment Modification
Financing Receivable, Modifications [Line Items]
Pre-modification, total modification	4,398,000
Post-modification, total modification	3,432,000
Payment Modification | Commercial | AQR Substandard
Financing Receivable, Modifications [Line Items]
Pre-modification, total modification	2,704,000
Post-modification, total modification	1,738,000
Payment Modification | Real estate term owner occupied | AQR Substandard
Financing Receivable, Modifications [Line Items]
Pre-modification, total modification	1,694,000
Post-modification, total modification	1,694,000
Combination Modification
Financing Receivable, Modifications [Line Items]
Pre-modification, total modification	0
Post-modification, total modification	0
Combination Modification | Commercial | AQR Substandard
Financing Receivable, Modifications [Line Items]
Pre-modification, total modification	0
Post-modification, total modification	0
Combination Modification | Real estate term owner occupied | AQR Substandard
Financing Receivable, Modifications [Line Items]
Pre-modification, total modification	0
Post-modification, total modification	$ 0