Summary of Significant Accounting Policies (Calculation Of Basic And Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Accounting Policies [Abstract]
Basic earnings per common share, Income (Numerator)	$ 81,005	$ 86,240	$ 158,502	$ 170,851
Shares used to compute basic earnings per share	161,795	166,152	162,404	166,423
Basic earnings per common share	$ 0.50	$ 0.52	$ 0.98	$ 1.03
Dilutive effect of stock options, income	$ 0	$ 0	$ 0	$ 0
Dilutive effect of stock options, shares	3,293	3,821	3,212	3,915
Diluted earnings per common share, Income (Numerator)	$ 81,005	$ 86,240	$ 158,502	$ 170,851
Shares used to compute diluted earnings per share	165,088	169,973	165,616	170,338
Diluted earnings per common share	$ 0.49	$ 0.51	$ 0.96	$ 1.00

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Amount of increase (decrease) to net income used for calculating diluted earnings per share (EPS), resulting from the assumed exercise of stock options or restrictive stock units (RSUs).

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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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Net Income or Loss Available to Common Stockholders plus adjustments resulting from the assumption that dilutive convertible securities were converted, options or warrants were exercised, or that other shares were issued upon the satisfaction of certain conditions.

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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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