Stockholder's Equity (Details) (USD $)	2 Months Ended	1 Months Ended		12 Months Ended
	Feb. 16, 2012	Feb. 11, 2011	Feb. 09, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Notes To Financial Statements [Abstract]
An aggregate maximum of shares of common stock authorized for repurchase				10,000,000
Remaining shares available for purchase under share repurchase authorization				6,386,200
Dividends Common Stock Cash	$ 0.17	$ 0.16	$ 0.155
Common Stock Dividends Declared				$ 0.64	$ 0.62	$ 0.58
Common Stock Issued Under Equity Compensation Plans				1,395,000	1,482,000	1,347,000
Treasury Stock Purchased				(267,000)	(115,000)	(168,000)
Common Stock Issued Under Employee Stock Purchase Plan				135,000	114,000	71,000
Treasury Stock Issued Under Other Equity Compensation Plans				109,000	87,000	177,000
Common Stock Sold				13,570,000
Common Shares Issued During Period				269,323,084	254,223,521	252,627,000	249,759,000
Common Stock Issued for Property Acquisition						1,450,000
Treasury Shares Outstanding				303,633	146,186	(118,000)	(127,000)
Common Shares Outstanding				269,019,000	254,077,000	252,509,000	249,632,000
Series E Junior Participating Preferred Stock (Series E)				1,500,000
Series E Junior Participating Preferred Stock (Series E), total following two-for-one stock split				3,000,000
Common Stock Activity [Abstract]
Shares of Common Stock Sold				13,570,000
Public Offering Price of Common Stock Sold				$ 105.50
Common Stock, Par (in dollars per share)				$ 0.01	$ 0.01
Proceeds From Issuance Or Sale Of Equity				$ 1,388,265,000	$ 0	$ 0