Earnings Per Share - Antidilutive Securities Excluded from Computation of EPS Table (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
5.75% Cumulative Convertible Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net Income Adjustments	$ 21	$ 21	$ 64	$ 64
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	59	56	59	56
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	47	47
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	42	39	42	40
5.0% Cumulative Convertible Preferred Stock Series Two Thousand And Five B [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net Income Adjustments	3	3	8	8
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	6	5	6	5
4.50% Cumulative Convertible Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net Income Adjustments	3	3	9	9
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	6	6	6	6
Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net Income Adjustments	$ 3	$ 3	$ 14	$ 14
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	3	2	3	3