Net Earnings Per Share Net Earnings Per Share (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Earnings Per Share [Abstract]
Net Income (loss) Available to Common Stockholders, Basic	$ 46,118	$ 71,563	$ 107,866	$ 110,758
Weighted Average Number of Shares Outstanding, Basic	135,519	137,749	135,530	138,124
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	1,565	2,400	1,575	2,440
Weighted Average Number of Shares Outstanding, Diluted	137,084	140,149	137,105	140,564

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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method.

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Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities; of income (loss) available to common shareholders.

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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.

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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.

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