Net Earnings Per Share Net Earnings Per Share (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Earnings Per Share [Abstract]
Net Income (loss) Available to Common Stockholders, Basic	$ 62,047	$ 73,151	$ 169,913	$ 183,909
Weighted Average Number of Shares Outstanding, Basic	134,741	138,190	135,264	138,146
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	1,309	2,137	1,562	2,467
Weighted Average Number of Shares Outstanding, Diluted	136,050	140,327	136,826	140,613

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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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