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Compensation Plans (Tables) | 12 Months Ended
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Dec. 31, 2020
Share-based Payment Arrangement [Abstract] |
Schedule of non-vested PSUs | A summary of the status and activity of non-vested PSUs is presented in the following table:
| For the Years Ended December 31,
| 2020 |  | 2019 |  | 2018
| PSUs (1) |  | Weighted-Average Grant-Date Fair Value |  | PSUs (1) |  | Weighted-Average Grant-Date Fair Value |  | PSUs (1) |  | Weighted-Average Grant-Date Fair Value
Non-vested at beginning of year | 2,022,585 |  |  | $ | 16.87 |  |  | 1,711,259 |  |  | $ | 20.68 |  |  | 1,533,491 |  |  | $ | 22.97 |
Granted | — |  | $ | — |  |  | 793,125 |  |  | $ | 12.80 |  |  | 572,924 |  |  | $ | 24.45 |
Vested | (792,572) |  |  | $ | 15.85 |  |  | (346,021) |  |  | $ | 26.32 |  |  | (233,102) |  |  | $ | 44.25 |
Forfeited | (399,549) |  |  | $ | 17.56 |  |  | (135,778) |  |  | $ | 16.98 |  |  | (162,054) |  |  | $ | 21.79 |
Non-vested at end of year | 830,464 |  |  | $ | 17.52 |  |  | 2,022,585 |  |  | $ | 16.87 |  |  | 1,711,259 |  |  | $ | 20.68 |
____________________________________________ (1)The number of shares of common stock assumes a multiplier of one. The actual final number of shares of common stock to be issued will range from zero to two times the number of PSUs awarded depending on the three-year performance multiplier.
Schedule of non-vested RSUs | A summary of the status and activity of non-vested RSUs granted to employees is presented in the following table:
| For the Years Ended December 31,
| 2020 |  | 2019 |  | 2018
| RSUs |  | Weighted- Average Grant-Date Fair Value |  | RSUs |  | Weighted- Average Grant-Date Fair Value |  | RSUs |  | Weighted- Average Grant-Date Fair Value
Non-vested at beginning of year | 1,532,131 |  |  | $ | 16.01 |  |  | 1,243,163 |  |  | $ | 21.50 |  |  | 1,244,262 |  |  | $ | 20.25 |
Granted | 1,458,869 |  |  | $ | 5.98 |  |  | 978,932 |  |  | $ | 12.36 |  |  | 583,552 |  |  | $ | 25.77 |
Vested | (746,132) |  |  | $ | 16.74 |  |  | (466,535) |  |  | $ | 21.94 |  |  | (407,529) |  |  | $ | 24.30 |
Forfeited | (147,008) |  |  | $ | 15.34 |  |  | (223,429) |  |  | $ | 18.16 |  |  | (177,122) |  |  | $ | 17.26 |
Non-vested at end of year | 2,097,860 |  |  | $ | 8.83 |  |  | 1,532,131 |  |  | $ | 16.01 |  |  | 1,243,163 |  |  | $ | 21.50 |
Schedule of shares settled, restricted stock units | A summary of the shares of common stock issued to settle employee RSUs is presented in the table below:
| For the Years Ended December 31,
| 2020 |  | 2019 |  | 2018
Shares of common stock issued to settle RSUs (1) | 746,132 |  |  | 466,535 |  |  | 407,529 |
Less: shares of common stock withheld for income and payroll taxes | (209,173) |  |  | (132,136) |  |  | (115,784) |
Net shares of common stock issued | 536,959 |  |  | 334,399 |  |  | 291,745 |
____________________________________________ (1) During the years ended December 31, 2020, 2019, and 2018, the Company issued shares of common stock to settle RSUs that related to awards granted in previous years. The Company and a majority of grant recipients mutually agreed to net share settle a portion of the awards to cover income and payroll tax withholdings in accordance with the Company’s Equity Plan and individual award agreements.
Schedule of employee stock purchase plan | The fair value of ESPP shares issued during the periods reported were estimated using the following weighted-average assumptions:
| For the Years Ended December 31,
| 2020 |  | 2019 |  | 2018
Risk free interest rate | 0.8 | % |  | 2.3 | % |  | 1.8 | %
Dividend yield | 0.7 | % |  | 0.7 | % |  | 0.4 | %
Volatility factor of the expected market price of the Company’s common stock | 166.2 | % |  | 56.6 | % |  | 55.9 | %
Expected life (in years) | 0.5 |  | 0.5 |  | 0.5

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- Definition Tabular disclosure of the changes in outstanding nonvested performance-based units. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition Tabular disclosure of the changes in outstanding nonvested restricted stock units. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition Tabular disclosure of the significant assumptions used during the year to estimate the fair value of employee stock purchase plans, including, but not limited to: (a) expected term, (b) expected volatility of the entity's shares, (c) expected dividends, (d) risk-free rate(s), and (e) discount for post-vesting restrictions. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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