Income Per Share (Details) - shares shares in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income per share:
Shares used to calculate basic income per share (in shares)	29,678	30,193	29,626	30,253
Dilutive effect of outstanding stock options, performance stock units and restricted stock units (in shares)	0	283	0	280
Shares used to calculate diluted income per share (in shares)	29,678	30,476	29,626	30,533
Stock options
Income per share:
Antidilutive securities excluded from computation of earnings per share, weighted average, amount (shares)	7	0	17	0
Anti-dilutive securities excluded from computation of diluted income per share (in shares)	94	5	104	11
Restricted stock units
Income per share:
Antidilutive securities excluded from computation of earnings per share, weighted average, amount (shares)	1	0	29	0
Anti-dilutive securities excluded from computation of diluted income per share (in shares)	305	0	227	2

Antidilutive Securities Excluded from Computation of Earnings Per Share, Weighted Average, Amount

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- Definition

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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- Definition

The sum of dilutive potential common shares or units used in the calculation of the diluted per-share or per-unit computation.

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- Definition

The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
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-Publisher FASB
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- Definition

Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
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