Earnings per Common Share (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Income (Numerator):
Net income	$ 193	$ 269	$ 396	$ 567
Earnings applicable to non-vested restricted stock	0	0	0	0
Net income applicable to common stock for computing basic earnings per common share	193	269	396	567
Net income as adjusted for purposes of computing diluted earnings per common share	$ 193	$ 269	$ 396	$ 567
Weighted average number of shares:
Outstanding during period (in shares)	572,240,000	607,755,000	575,218,000	615,138,000
Non-vested restricted stock (in shares)	(4,325,000)	(3,453,000)	(3,993,000)	(3,276,000)
Weighted average shares outstanding for computing basic (loss) earnings per common share (in shares)	567,915,000	604,302,000	571,225,000	611,862,000
Incremental common shares attributable to dilutive securities:
Shares issuable under convertible securities (in shares)	10,000	10,000	10,000	10,000
Shares issuable under incentive compensation plans (in shares)	1,107,000	1,290,000	1,009,000	1,466,000
Number of shares as adjusted for purposes of computing diluted (loss) earnings per common share (in shares)	569,032,000	605,602,000	572,244,000	613,338,000
Basic earnings per common share:
Basic (loss) earnings per common share (in dollars per share)	$ 0.34	$ 0.45	$ 0.69	$ 0.93
Diluted earnings per common share:
Diluted (loss) earnings per common share (in dollars per share)	$ 0.34	$ 0.44	$ 0.69	$ 0.92
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)	2,400,000	2,400,000	2,800,000	2,400,000