|
Short-term Investments (Details) (USD $)
|
Dec. 31, 2014
|
Dec. 31, 2013
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Short-term investments |
$ 45,621,593 |
$ 27,084,980 |
| Certificates of Deposit [Member] | Maturity date of February 26, 2015 [Member] |
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Short-term investments |
23,500,000 |
|
| Certificates of Deposit [Member] | Maturity date of April 23, 2015 [Member] |
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Short-term investments |
10,000,000 |
|
| Certificates of Deposit [Member] | Maturity date of April 30, 2015 [Member] |
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Short-term investments |
$ 12,100,000 |
|