Earnings Per Share (Schedule Of Net Income Attributable To Common Stockholders) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Earnings Per Share [Abstract]
Net income	$ 87,813	$ 83,544
Less: Net income attributable to participating securities	(610)	(778)
Net income attributable to common shareholders	$ 87,203	$ 82,766