Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Earnings Per Share
Antidilutive common share equivalents excluded from computation of earnings per share amount (in shares)	0	0
Net Income (Numerator)
Basic earnings per share (in dollars)	$ 204,328	$ 227,551
Diluted earnings per share (in dollars)	$ 204,328	$ 227,551
Weighted Average Shares (Denominator)
Basic earnings per share (in shares)	224,058,000	236,623,000
Dilutive common share equivalents (in shares)	904,000	1,100,000
Diluted earnings per share (in shares)	224,962,000	237,723,000
Per Share Amount
Basic (in dollars per share)	$ 0.91	$ 0.96
Diluted (in dollars per share)	$ 0.91	$ 0.96

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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The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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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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