Earnings (Loss) per Common Share (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Income (Numerator):
Net income (loss)	$ 188	$ (1,045)	$ 584	$ (478)
Earnings applicable to non-vested restricted stock	0	0	0	0
Net income (loss) applicable to common stock for computing basic earnings (loss) per common share	188	(1,045)	584	(478)
Net income (loss) as adjusted for purposes of computing diluted earnings (loss) per common share	$ 188	$ (1,045)	$ 584	$ (478)
Weighted average number of shares:
Outstanding during period (in shares)	570,545,000	598,350,000	573,661,000	609,542,000
Non-vested restricted stock (in shares)	(4,580,000)	(3,763,000)	(4,189,000)	(3,438,000)
Weighted average shares outstanding for computing basic (loss) earnings per common share (in shares)	565,965,000	594,587,000	569,472,000	606,104,000
Incremental common shares attributable to dilutive securities:
Shares issuable under convertible securities (in shares)	10,000	0	10,000	0
Shares issuable under incentive compensation plans (in shares)	1,457,000	0	1,158,000	0
Number of shares as adjusted for purposes of computing diluted (loss) earnings per common share (in shares)	567,432,000	594,587,000	570,640,000	606,104,000
Basic earnings per common share:
Basic earnings (loss) per common share (in dollars per share)	$ 0.33	$ (1.76)	$ 1.03	$ (0.79)
Diluted earnings per common share:
Diluted earnings (loss) per common share (in dollars per share)	$ 0.33	$ (1.76)	$ 1.02	$ (0.79)
Stock option awards
Diluted earnings per common share:
Number of shares of common stock excluded from the computation of diluted earnings per share (in shares)	2,100,000	2,700,000	2,500,000	2,500,000
Share-based payments and convertible debt securities
Diluted earnings per common share:
Number of shares of common stock excluded from the computation of diluted earnings per share (in shares)		1,160,000		1,370,000