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Stockholders' Equity Stockholders' Equity (Tables) | 12 Months Ended
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Dec. 31, 2016
Equity [Abstract] |
Nonvested stock rollforward | Activity under the Company’s nonvested stock awards and restricted share units for the years ended December 31, 2016, 2015, and 2014 was as follows:
(Shares in thousands, $ in millions) |  | 2016 |  | 2015 |  | 2014
|  | Number of shares/units |  | Weighted Average Grant Date Fair Value |  | Number of shares |  | Weighted Average Grant Date Fair Value |  | Number of shares |  | Weighted Average Grant Date Fair Value
Nonvested, beginning of year |  | 1,652 |  |  | $ | 57.0 |  |  | 1,376 |  |  | $ | 47.8 |  |  | 927 |  |  | $ | 36.9 |
Granted |  | 682 |  |  | 8.4 |  |  | 669 |  |  | 20.8 |  |  | 675 |  |  | 20.3 |
Vested |  | (154 | ) |  | (4.3 | ) |  | (23 | ) |  | (0.8 | ) |  | (18 | ) |  | (1.0 | )
Forfeited |  | (328 | ) |  | (9.6 | ) |  | (370 | ) |  | (10.8 | ) |  | (208 | ) |  | (8.4 | )
Nonvested, end of year |  | 1,852 |  |  | $ | 51.5 |  |  | 1,652 |  |  | $ | 57.0 |  |  | 1,376 |  |  | $ | 47.8 |
TSR Award Performance | The estimated fair value of each TSR award, the projected shares to be awarded and future compensation expense to be recognized for these awards, including actual and estimated forfeitures, was as follows: (Shares in thousands, $ in millions)
TSR Award Performance Period |  | Award Fair Value |  | December 31, 2016 Unrecognized Compensation Expense |  | Minimum Shares |  | Target Shares |  | Maximum Shares
2014 - 2016 |  | $ | 8.9 |  |  | $ | — |  |  | — |  |  | 262 |  |  | 524 |
2015 - 2017 |  | $ | 12.5 |  |  | 4.2 |  |  | — |  |  | 276 |  |  | 552 |
Total |  |  |  | $ | 4.2 |  |  | — |  |  | 538 |  |  | 1,076 |

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- Definition Disclosure of the number and weighted-average grant date fair value for restricted stock and restricted stock units that were outstanding at the beginning and end of the year, and the number of restricted stock and restricted stock units that were granted, vested, or forfeited during the year. + References No definition available. + Details
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