Employee Equity Incentive Plans (Tables)
|6 Months Ended|
Jun. 30, 2018
|Employee Benefits and Share-based Compensation, Noncash [Abstract]|
|Schedule of Share-based Compensation, Restricted Stock Units Award Activity [Table Text Block]||
Restricted stock unit activity in the first six months of 2018 was as follows:
Tabular disclosure of the number and weighted-average grant date fair value for restricted stock units that were outstanding at the beginning and end of the year, and the number of restricted stock units that were granted, vested, or forfeited during the year.
Reference 1: http://www.xbrl.org/2003/role/presentationRef