Earnings Per Share (Schedule Of Net Income Attributable To Common Stockholders) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Earnings Per Share [Abstract]
Net income	$ 95,277	$ 86,964	$ 115,501	$ 87,813	$ 26,443	$ 67,930	$ 81,049	$ 83,544	$ 385,555	$ 258,966	$ 221,393
Less: Net income attributable to participating securities									(2,160)	(2,310)	(2,230)
Net income attributable to common shareholders									$ 383,395	$ 256,656	$ 219,163