|
Current and future income taxes - Taxable income (Details) (USD $)
|
Dec. 31, 2013
|
|---|---|
|
2029
|
|
| Income Tax Disclosure [Line Items] | |
| Tax credit carryforward, amount | $ 65,242 |
|
2030
|
|
| Income Tax Disclosure [Line Items] | |
| Tax credit carryforward, amount | 1,102,400 |
|
2031
|
|
| Income Tax Disclosure [Line Items] | |
| Tax credit carryforward, amount | 1,159,614 |
|
2033
|
|
| Income Tax Disclosure [Line Items] | |
| Tax credit carryforward, amount | $ 4,275,931 |