Revenue (Tables) |
3 Months Ended | |||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Mar. 31, 2018 | ||||||||||||||||||||||
| Revenue from Contract with Customer [Abstract] | ||||||||||||||||||||||
| Deferred Revenue, by Arrangement, Disclosure [Table Text Block] |
Activity in the deferred revenue account was as follows:
|
| X | ||||||||||
- Definition Tabular disclosure of the type of arrangements and the corresponding amounts that comprise the current and noncurrent balance of deferred revenue as of the balance sheet date. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
- References No definition available.
|