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Share-Based Compensation - Stock Option Plans (Details) $ / shares in Units, $ in Thousands |  |  | 12 Months Ended
--- | --- | --- | ---
Apr. 22, 2020 | Apr. 20, 2020 | Dec. 31, 2020 USD ($) item $ / shares shares | Dec. 31, 2019 USD ($) $ / shares shares | Dec. 31, 2018 USD ($) $ / shares shares | Dec. 31, 2017 USD ($)
Share-based compensation disclosures |  |  |  |  |  |
Share-based compensation expense | $ |  |  | $ 24,600 | $ 24,700 | $ 26,400 |
Reverse stock split ratio | 50 | 0.02 |  |  |  |
Liability related to awards | $ |  |  | $ 82,462 | 97,003 |  |
Options |  |  |  |  |  |
Options awarded (in shares) |  |  | 0 |  |  |
Restricted Stock |  |  |  |  |  |
Share-based compensation disclosures |  |  |  |  |  |
Share-based compensation expense | $ |  |  | $ 23,600 | $ 24,500 | $ 26,000 |
Number of types of performance share awards | item |  |  | 2 |  |  |
Option to purchase common stock available for grant |  |  | 400,000 |  |  |
Granted (in shares) |  |  | 4,000 |  |  |
Shares awarded during period |  |  | 4,000 |  |  |
Restricted Stock | Employees and Director |  |  |  |  |  |
Share-based compensation disclosures |  |  |  |  |  |
Granted (in shares) |  |  | 4,156 | 65,299 | 47,850 |
Shares awarded during period |  |  | 4,156 | 65,299 | 47,850 |
Aggregate value of restricted stock awards at date of grant | $ |  |  | $ 100 | $ 10,600 | $ 16,600 |
Fair value of awards vested | $ |  |  | $ 2,600 | $ 4,100 | $ 8,700 |
Restricted Stock | Maximum |  |  |  |  |  |
Share-based compensation disclosures |  |  |  |  |  |
Vesting period of shares |  |  | 5 years |  |  |
Restricted Stock | Maximum | Employees and Director |  |  |  |  |  |
Share-based compensation disclosures |  |  |  |  |  |
Vesting period of shares |  |  | 4 years | 4 years | 4 years |
Restricted Stock Based on Performance Conditions |  |  |  |  |  |
Share-based compensation disclosures |  |  |  |  |  |
Granting period |  |  | 1 year |  |  |
Restricted Stock Based on Performance Conditions | Executive Officers |  |  |  |  |  |
Share-based compensation disclosures |  |  |  |  |  |
Vesting period of shares |  |  | 3 years | 3 years | 3 years |
Total fair value of option vested during the period | $ |  |  | $ 3,000 | $ 2,500 | $ 4,800 |
Granted (in shares) |  |  | 59,490 | 48,253 | 20,199 |
Shares awarded during period |  |  | 59,490 | 48,253 | 20,199 |
Liability related to awards | $ |  |  | $ 2,400 | $ 2,400 |  |
Fair value of awards vested | $ |  |  |  | $ 8,800 | $ 7,500 | $ 7,000
Restricted Stock Based on Performance Conditions | Maximum |  |  |  |  |  |
Share-based compensation disclosures |  |  |  |  |  |
Vesting percentage |  |  | 200.00% |  |  |
Restricted Stock Based on Performance Conditions | Minimum |  |  |  |  |  |
Share-based compensation disclosures |  |  |  |  |  |
Vesting percentage |  |  | 30.00% |  |  |
Restricted Stock Based on Market Conditions |  |  |  |  |  |
Share-based compensation disclosures |  |  |  |  |  |
Vesting period of shares |  |  | 3 years | 3 years | 3 years |
Granted (in shares) |  |  | 22,931 | 52,191 | 21,163 |
Shares awarded during period |  |  | 22,931 | 52,191 | 21,163 |
Aggregate value of restricted stock awards at date of grant | $ |  |  | $ 3,400 | $ 3,700 | $ 5,100 |
Assumptions used to value grant date fair value |  |  |  |  |  |
Risk free interest rate (as a percent) |  |  | 1.57% | 2.48% | 2.02% |
Expected volatility (as a percent) |  |  | 74.00% | 70.00% | 57.00% |
Share price | $ / shares |  |  | $ 148.00 | $ 109.50 | $ 343.50 |
Expected term (in years) |  |  | 3 years | 3 years | 3 years |
Key Officer Director and Managerial Employee Stock Options |  |  |  |  |  |
Share-based compensation disclosures |  |  |  |  |  |
Option to purchase common stock available for grant |  |  | 400,000 | 200,000 |  |
Exercise period |  |  | 10 years |  |  |
Total fair value of option vested during the period | $ |  |  |  | $ 200 | $ 400 |
Options |  |  |  |  |  |
Options outstanding at the beginning of the period (in shares) |  |  | 33,000 |  |  |
Exercised (in shares) |  |  | 0 | 0 | 0 |
Surrendered (in shares) |  |  | (1,000) |  |  |
Forfeited (in shares) |  |  | (1,000) |  |  |
Options outstanding at the end of the period (in shares) |  |  | 31,000 | 33,000 |  |
Options exercisable at the end of the period (in shares) |  |  | 31,000 |  |  |
Weighted Average Exercise Price |  |  |  |  |  |
Options outstanding at the beginning of the period (in dollars per share) | $ / shares |  |  | $ 638.63 |  |  |
Surrendered (in dollars per share) | $ / shares |  |  | 964.17 |  |  |
Forfeited (in dollars per share) | $ / shares |  |  | 718.53 |  |  |
Options outstanding at the end of the period (in dollars per share) | $ / shares |  |  | 628.10 | $ 638.63 |  |
Options exercisable at the end of the period (in dollars per share) | $ / shares |  |  | $ 628.10 |  |  |
Weighted Average Remaining Contractual Term |  |  |  |  |  |
Options outstanding at the end of the period |  |  | 3 years 4 months 24 days |  |  |
Options exercisable at the end of the period |  |  | 3 years 4 months 24 days |  |  |
Assumptions used to value grant date fair value |  |  |  |  |  |
Granted (in dollars per share) | $ / shares |  |  |  | $ 53.50 | $ 87.50 |
Risk free interest rate (as a percent) |  |  |  | 1.79% | 2.59% |
Dividend yield (as a percent) |  |  |  | 1.65% | 3.03% |
Expected volatility (as a percent) |  |  |  | 57.59% | 57.11% |
Expected term (in years) |  |  |  | 4 years | 4 years |
Key Officer Director and Managerial Employee Stock Options | Employees Executives And Directors |  |  |  |  |  |
Share-based compensation disclosures |  |  |  |  |  |
Vesting period of shares |  |  | 4 years | 4 years | 4 years |
Options |  |  |  |  |  |
Granted (in shares) |  |  |  | 2,759 | 3,422 |

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