Quarterly Financial Information (unaudited) (Tables)
|12 Months Ended|
Dec. 31, 2017
|Quarterly Financial Information (Unaudited) [Abstract]|
|Schedule of Quarterly Financial Information [Table Text Block]||
Tabular disclosure of quarterly financial data. Includes, but is not limited to, financial information for fiscal quarters, cumulative effect of a change in accounting principle and earnings per share data.
Reference 1: http://www.xbrl.org/2003/role/presentationRef