Business and summary of significant accounting policies - Income taxes and advertising expense (Details) - USD ($) |
1 Months Ended | 12 Months Ended | |
|---|---|---|---|
Jun. 30, 2015 |
Dec. 31, 2016 |
Dec. 31, 2015 |
|
| Organization, Consolidation and Presentation of Financial Statements [Abstract] | |||
| Decrease in valuation allowance | $ 7,700,000 | $ 12,000,000 | |
| Unrecognized tax benefits | 0 | $ 0 | |
| Advertising expense | $ 3,200,000 | $ 2,400,000 | |
| X | ||||||||||
- Definition Amount charged to advertising expense for the period, which are expenses incurred with the objective of increasing revenue for a specified brand, product or product line. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
- References No definition available.
|
| X | ||||||||||
- Definition Amount of unrecognized tax benefits. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
- Definition Amount of increase (decrease) in the valuation allowance for a specified deferred tax asset. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|