Warrants (May Investors) (Details) - USD ($) $ / shares in Units, $ in Millions |
6 Months Ended | 12 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
Jan. 30, 2009 |
|
| Class of Warrant or Right [Line Items] | ||||
| Exercise price of warrants (in usd per share) | $ 10.00 | |||
| Arrearage on dividend payments | $ 102 | |||
| Series C Preferred Stock | ||||
| Class of Warrant or Right [Line Items] | ||||
| Preferred stock, dividend rate, percentage | 9.00% | 9.00% | ||
| May Investors | ||||
| Class of Warrant or Right [Line Items] | ||||
| Warrants exercised to purchase Common Stock (shares) | 0 | 72,945 | ||
| Common Stock issued (shares) | 42,101 | |||
| Warrants outstanding (shares) | 615,962 | 615,962 | ||
| Exercise price of warrants (in usd per share) | $ 10 | $ 10.00 | ||
| Warrant liabilities | $ 9 | $ 8 | $ 6 | |
| Troubled Asset Relief Program | ||||
| Class of Warrant or Right [Line Items] | ||||
| Exercise price of warrants (in usd per share) | $ 62.00 | $ 62.00 | ||
| Warrants to purchase Common Stock issued (shares) | 645,138 | 645,138 | ||
| Arrearage on dividend payments | $ 86 |