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Stockholders' Equity (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Apr. 30, 1997
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common shares repurchased under repurchase program	200,000
Cost of common shares repurchased	$ 22,800
Total number of shares repurchased pursuant to the repurchase program	41,836,234	41,636,234
Total cost of shares repurchased pursuant to the repurchase program	$ 1,623,256	$ 1,600,412
Additional shares that can be repurchased under the approved share repurchase program	12,900,000
Preferred stock, shares authorized	2,000,000	2,000,000
Preferred stock at par value	$ 0.01	$ 0.01
Preferred stock, shares issued	0	0
Series A Junior Participating Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred stock, shares authorized			2,000,000
Preferred stock at par value			$ 0.01
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
2009 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period	7 years
Common stock authorized for issuance	51,100,000
Number of securities remaining available for future issuance	17,800,000
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of securities remaining available for future issuance	500,000
Minimum [Member] \| 2009 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	1 year
Maximum [Member] \| 2009 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	4 years