Loans and Credit Quality - Newly Restructured Loans (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) contract
Financing Receivable, Modifications [Line Items]
Pre-modification, number of contracts | contract	3
Pre-modification, total modification	$ 12,953
Post-modification, number of contracts | contract	3
Post-modification, total modification	$ 10,610
Commercial | Asset Quality Rating - Special Mention
Financing Receivable, Modifications [Line Items]
Pre-modification, number of contracts | contract	1
Pre-modification, total modification	$ 2,078
Post-modification, number of contracts | contract	1
Post-modification, total modification	$ 2,059
Commercial | Asset Quality Rating - Substandard
Financing Receivable, Modifications [Line Items]
Pre-modification, number of contracts | contract	2
Pre-modification, total modification	$ 10,875
Post-modification, number of contracts | contract	2
Post-modification, total modification	$ 8,551
Rate Modification
Financing Receivable, Modifications [Line Items]
Pre-modification, total modification	0
Post-modification, total modification	0
Rate Modification | Commercial | Asset Quality Rating - Special Mention
Financing Receivable, Modifications [Line Items]
Pre-modification, total modification	0
Post-modification, total modification	0
Rate Modification | Commercial | Asset Quality Rating - 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	12,743
Post-modification, total modification	10,408
Term Modification | Commercial | Asset Quality Rating - Special Mention
Financing Receivable, Modifications [Line Items]
Pre-modification, total modification	2,078
Post-modification, total modification	2,059
Term Modification | Commercial | Asset Quality Rating - Substandard
Financing Receivable, Modifications [Line Items]
Pre-modification, total modification	10,665
Post-modification, total modification	8,349
Payment Modification
Financing Receivable, Modifications [Line Items]
Pre-modification, total modification	210
Post-modification, total modification	202
Payment Modification | Commercial | Asset Quality Rating - Special Mention
Financing Receivable, Modifications [Line Items]
Pre-modification, total modification	0
Post-modification, total modification	0
Payment Modification | Commercial | Asset Quality Rating - Substandard
Financing Receivable, Modifications [Line Items]
Pre-modification, total modification	210
Post-modification, total modification	202
Combination Modification
Financing Receivable, Modifications [Line Items]
Pre-modification, total modification	0
Post-modification, total modification	0
Combination Modification | Commercial | Asset Quality Rating - Special Mention
Financing Receivable, Modifications [Line Items]
Pre-modification, total modification	0
Post-modification, total modification	0
Combination Modification | Commercial | Asset Quality Rating - Substandard
Financing Receivable, Modifications [Line Items]
Pre-modification, total modification	0
Post-modification, total modification	$ 0