Net Income Per Share (Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Unvested Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares	4	8
Outstanding Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares	1	1
5.75% Cumulative Convertible Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net Income Adjustments	22	22
Shares	55	56
Interest rate	5.75%	5.75%
5.75% Cumulative Convertible Preferred Stock (Series A) [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net Income Adjustments	16	16
Shares	39	39
Interest rate	5.75%	5.75%
5.00% Cumulative Convertible Preferred Stock (Series 2005B) [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net Income Adjustments	3	3
Shares	5	5
Interest rate	5.00%	5.00%
4.50% Cumulative Convertible Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net Income Adjustments	3	3
Shares	6	6
Interest rate	4.50%	4.50%