Restructuring - (Narrative) (Details) - USD ($) $ in Thousands  | 
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2017  | 
Dec. 31, 2016  | 
Dec. 31, 2015  | 
|
| Restructuring Cost and Reserve [Line Items] | |||
| Restructuring charges | $ 160 | $ 1,395 | $ 3,375 | 
| 2014 Plan [Member] | |||
| Restructuring Cost and Reserve [Line Items] | |||
| Restructuring charges | 0 | 30 | 2,356 | 
| Cumulative restructuring charges | 5,969 | ||
| 2015 Plan [Member] | |||
| Restructuring Cost and Reserve [Line Items] | |||
| Restructuring charges | 160 | $ 1,365 | $ 1,019 | 
| Cumulative restructuring charges | $ 2,544 | ||
| X | ||||||||||
- Definition Restructuring Charges, Cumulative No definition available. 
  | 
| X | ||||||||||
- Definition Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
  | 
| X | ||||||||||
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available. 
  | 
| X | ||||||||||
- Details 
  | 
| X | ||||||||||
- Details 
  |