Stockholders' Equity (Preferred Stock) (Details) - USD ($) |
6 Months Ended | 12 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
Jan. 30, 2009 |
|
| Class of Stock [Line Items] | ||||
| Preferred stock, par value (in usd per share) | $ 0.01 | $ 0.01 | $ 0.01 | |
| Preferred stock, liquidation value per share (in usd per share) | $ 1,000 | $ 1,000 | $ 1,000 | |
| Shares Outstanding | 266,657 | 266,657 | 266,657 | |
| Series C Preferred Stock | ||||
| Class of Stock [Line Items] | ||||
| Dividend rate (percent) | 9.00% | 9.00% | ||
| Shares Outstanding | 266,657 | 266,657 | 266,657 | |
| Preferred Shares | $ 267,000,000 | $ 0 | ||
| Preferred Stock | $ 267,000,000 | $ 267,000,000 |