Earnings Per Share - Antidilutive Securities Excluded from Computation of EPS Table (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Basic	$ 0.73	$ (1.46)	$ 2.47
Diluted	$ 0.73	$ (1.46)	$ 2.32
Basic	653	643	637
Weighted Average Number of Shares Outstanding, Diluted	653	643	752
Convertible Debt Securities [Member] | 5.75% Cumulative Convertible Preferred Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net Income Adjustments	$ 86	$ 86
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	56	56
Convertible Debt Securities [Member] | 5.75% Cumulative Convertible Preferred Stock Series A
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net Income Adjustments	63	63
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	40	39
Convertible Debt Securities [Member] | 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	10	10
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	5	5
Convertible Debt Securities [Member] | 4.50% Cumulative Convertible Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net Income Adjustments	12	12
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	6	6
Restricted stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net Income Adjustments	$ 10	$ 0
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	5	5