|
Income taxes (Details 2) (USD $)
|
12 Months Ended |
|---|---|
|
Dec. 31, 2014
|
|
| Tax credit carryforwards | |
| Testing period for changes in ownership interest of significant shareholders | 3 years |
| Federal | |
| Tax credit carryforwards | |
| Tax credits | 2,300,000 |
| State | |
| Tax credit carryforwards | |
| Tax credits | 842,000 |