Stock-based Compensation (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Stock-Based Compensation
Grant date fair value	$ 102	$ 100	$ 25,865	$ 26,741
Stock-based compensation expense	$ 8,941	$ 8,532	$ 19,124	$ 20,766
Stock Options
Stock-Based Compensation
Granted (in units)			344	674
Grant date fair value			$ 2,965	$ 6,147
Exercised (in units)	127	55	245	285
Performance-based RSUs
Stock-Based Compensation
Granted (in units)			665	524
Grant date fair value			$ 15,253	$ 12,791
Vested (in units)			648	774
Time-based RSUs
Stock-Based Compensation
Granted (in units)	4	5	334	321
Grant date fair value	$ 102	$ 100	$ 7,647	$ 7,803
Vested (in units)	3	1	294	245

Fair value of share-based payments awards options and other than options granted.

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- Definition

Fair value of share-based payments awards options granted.

+ References

No definition available.

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- Definition

Fair value of share-based payments awards other than options granted.

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- Definition

Number of options exercised.

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- Definition

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5047-113901

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
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-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

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- Definition

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).

+ 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
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-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

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- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

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

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