Equity Compensation Plans - Outstanding and Exercisable Options and Restricted Stock (Details) shares in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2020 $ / shares shares	Jun. 30, 2020 $ / shares shares
Stock Options
Shares
Outstanding at beginning of period (shares)	761	683
Granted (shares)	58	169
Exercised (shares)	0	(4)
Forfeited or Expired (shares)	(71)	(100)
Outstanding at end of period (shares)	748	748
Exercisable (shares)	297	297
Unvested (shares)	451	451
Weighted- Average Exercise Price
Outstanding at beginning of period (USD per share) \| $ / shares	$ 26.35	$ 27.15
Granted (USD per share) \| $ / shares	9.41	17.44
Exercised (USD per share) \| $ / shares	0	8.67
Forfeited or Expired (USD per share) \| $ / shares	22.85	24.91
Outstanding at end of period (USD per share) \| $ / shares	25.36	25.36
Exercisable (USD per share) \| $ / shares	33.80	33.80
Unvested (USD per share) \| $ / shares	$ 19.79	$ 19.79
Time-Based Restricted Stock
Restricted Stock
Unvested at beginning of period (shares)	203	159
Granted (shares)	23	77
Vested (shares)	0	(3)
Forfeited or Expired (shares)	(6)	(13)
Unvested at end of period (shares)	220	220
Performance-Based Restricted Stock Awards
Restricted Stock
Unvested at beginning of period (shares)	154	129
Granted (shares)	25	66
Vested (shares)	0	0
Forfeited or Expired (shares)	(18)	(34)
Unvested at end of period (shares)	161	161

The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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For presentations that combine terminations, the number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan or that expired.

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Weighted average price of options that were either forfeited or expired.

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Gross number of share options (or share units) granted during the period.

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Number of options outstanding, including both vested and non-vested options.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Number of fully vested and expected to vest options outstanding that can be converted into shares under option plan. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Weighted-average exercise price, at which grantee can acquire shares reserved for issuance, for fully vested and expected to vest options outstanding. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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Number of share options (or share units) exercised during the current period.

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