Stockholders’ and Mezzanine equity - Equity Distribution Agreement (Details) - USD ($) $ in Thousands, shares in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2015 |
May 24, 2016 |
|
| Common Stock | |||
| Proceeds from sale of common stock | $ 65,446 | $ 122,779 | |
| Class A common stock | |||
| Common Stock | |||
| Offering value to sell common stock shares under equity distribution agreement | $ 73,000 | ||
| Proceeds from sale of common stock | 1,800 | ||
| Gross proceeds from sale of common stock | 2,100 | ||
| Professional services expenses | 300 | ||
| Aggregate offering price | $ 70,900 | ||
| Common Stock | Class A common stock | |||
| Common Stock | |||
| Sale of stock (in shares) | 0.5 | ||