Earnings Per Share (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Basic:
Net income	$ 97	$ 35
Basic weighted-average shares outstanding (in thousands)	288,051,000	286,626,000
Basic earnings per share (in dollars per share)	$ 0.34	$ 0.12
Diluted:
Net income	$ 97	$ 35
Basic weighted-average shares outstanding (in thousands)	288,051,000	286,626,000
Effect of dilutive securities:
Weighted-average convertible debentures (in thousands)	4,080,000	4,125,000
Weighted-average options and restricted stock issued to employees (in thousands)	1,688,000	945,000
Diluted weighted-average shares outstanding (in thousands)	293,819,000	291,696,000
Diluted earnings per share (in dollars per share)	$ 0.33	$ 0.12
Antidilutive Securities Excluded From Computations Of Earnings Per Share [Abstract]
Other stock options and restricted stock awards and units	700,000	2,700,000