Securities (Financing Receivable Credit Quality Indicators) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment [Line Items]
Amount	$ 162,987	$ 157,830
Standard Poor's, AAA Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Amount	162,336	156,947
Standard Poor's, BB Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Amount	651	411
Standard Poor's, B+ Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Amount		$ 472

Investments in notes or bonds that are collateralized by a specific group of underlying assets owned by the issuer of the notes or bonds which are short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three-years ago does not become a cash equivalent when its remaining maturity is three months.

No definition available.

Name:	us-gaap_AssetBackedSecuritiesAtCarryingValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant