Loans and Credit Quality - Troubled Debt Restructured Loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Modifications [Line Items]
New Troubled Debt Restructurings	$ 10,610
Existing Troubled Debt Restructurings	13,237
Total	23,847	$ 16,200
Commercial | Asset Quality Rating - Special Mention
Financing Receivable, Modifications [Line Items]
New Troubled Debt Restructurings	2,059
Commercial | Asset Quality Rating - Substandard
Financing Receivable, Modifications [Line Items]
New Troubled Debt Restructurings	8,551
Accrual Status
Financing Receivable, Modifications [Line Items]
New Troubled Debt Restructurings	2,261
Existing Troubled Debt Restructurings	5,407
Total	7,668
Accrual Status | Commercial | Asset Quality Rating - Special Mention
Financing Receivable, Modifications [Line Items]
New Troubled Debt Restructurings	2,059
Accrual Status | Commercial | Asset Quality Rating - Substandard
Financing Receivable, Modifications [Line Items]
New Troubled Debt Restructurings	202
Nonaccrual Status
Financing Receivable, Modifications [Line Items]
New Troubled Debt Restructurings	8,349
Existing Troubled Debt Restructurings	7,830
Total	16,179
Nonaccrual Status | Commercial | Asset Quality Rating - Special Mention
Financing Receivable, Modifications [Line Items]
New Troubled Debt Restructurings	0
Nonaccrual Status | Commercial | Asset Quality Rating - Substandard
Financing Receivable, Modifications [Line Items]
New Troubled Debt Restructurings	$ 8,349