Earnings (Loss) Per Share (Details) - USD ($) $ / shares in Units, $ in Millions |
3 Months Ended | 6 Months Ended | 12 Months Ended | |||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Jun. 30, 2016 |
Dec. 31, 2015 |
Sep. 30, 2015 |
Jun. 30, 2015 |
Mar. 31, 2015 |
Dec. 31, 2014 |
Sep. 30, 2014 |
Jun. 30, 2014 |
Mar. 31, 2014 |
Dec. 31, 2013 |
Sep. 30, 2013 |
Jun. 30, 2013 |
Mar. 31, 2013 |
Jun. 30, 2016 |
Jun. 30, 2015 |
Dec. 31, 2015 |
Dec. 31, 2014 |
Dec. 31, 2013 |
|
| Earnings Per Share [Abstract] | ||||||||||||||||||
| Net income (loss) | $ 47 | $ 46 | $ 11 | $ (28) | $ 26 | $ (78) | $ 162 | $ 14 | $ 67 | $ 23 | $ 86 | $ 78 | $ 158 | $ (69) | $ 267 | |||
| Less: preferred stock dividend/accretion | $ 0 | $ 0 | $ 0 | $ (1) | $ (2) | $ (1) | $ (1) | $ (1) | 0 | (1) | (6) | |||||||
| Net income (loss) from continuing operations | 158 | (70) | 261 | |||||||||||||||
| Deferred cumulative preferred stock dividends | (8) | (7) | (16) | (15) | (30) | (26) | (14) | |||||||||||
| Net income (loss) applicable to Common Stockholders | $ 39 | $ 39 | $ 70 | $ 63 | $ 128 | $ (96) | $ 247 | |||||||||||
| Weighted Average Shares | ||||||||||||||||||
| Weighted average common shares outstanding | 56,574,796 | 56,436,026 | 56,544,256 | 56,410,880 | 56,426,977 | 56,246,528 | 56,063,282 | |||||||||||
| Effect of dilutive securities | ||||||||||||||||||
| May Investor Warrants (in shares) | 349,539 | 299,391 | 327,307 | 266,118 | 305,484 | 0 | 237,412 | |||||||||||
| Stock-based Awards (in shares) | 826,895 | 429,655 | 751,518 | 294,135 | 432,062 | 0 | 217,487 | |||||||||||
| Weighted average diluted common shares (in shares) | 57,751,230 | 57,165,072 | 57,623,081 | 56,971,133 | 57,164,523 | 56,246,528 | 56,518,181 | |||||||||||
| Earnings (loss) per common share | ||||||||||||||||||
| Basic earnings (loss) per common share (in usd per share) | $ 0.67 | $ 0.45 | $ 0.70 | $ 0.69 | $ 0.43 | $ 0.07 | $ (0.61) | $ 0.33 | $ (1.51) | $ 2.79 | $ 0.16 | $ 1.11 | $ 0.33 | $ 1.23 | $ 1.12 | $ 2.27 | $ (1.72) | $ 4.40 |
| Effect of dilutive securities | ||||||||||||||||||
| Effect of dilutive securities - May Investor Warrants (in usd per share) | (0.01) | (0.00) | (0.02) | |||||||||||||||
| Effect of dilutive securities - Stock-based awards (in usd per share) | 0.01 | 0.01 | 0.02 | 0.01 | (0.02) | (0.00) | (0.01) | |||||||||||
| Diluted (loss) earnings per share (in usd per share) | 0.66 | $ 0.44 | $ 0.69 | $ 0.68 | $ 0.43 | $ 0.07 | $ (0.61) | $ 0.33 | $ (1.51) | $ 2.77 | $ 0.16 | $ 1.10 | $ 0.33 | 1.21 | $ 1.11 | $ 2.24 | $ (1.72) | $ 4.37 |
| Exercise price of warrants (in usd per share) | $ 10.00 | $ 10.00 | ||||||||||||||||
| Fair value of warrants | $ 8 | $ 11 | $ 8 | $ 11 | ||||||||||||||