Earnings Per Common Share (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Income (Numerator):
Net income	$ 200	$ 211
Earnings applicable to non-vested restricted stock		(2)
Net income applicable to common stock for computing basic earnings per common share	200	209
Net income as adjusted for purposes of computing diluted earnings per common share	$ 200	$ 209
Weighted average number of shares:
Outstanding during period (in shares)	619,740,000	305,384,000
Non-vested restricted stock (in shares)	(2,544,000)	(2,009,000)
Non-vested restricted stock units (in shares)	1,012,000	457,000
Weighted average shares outstanding for computing basic earnings per common share	618,208,000	303,832,000
Incremental common shares attributable to dilutive securities:
Shares issuable under convertible securities	13,000	13,000
Shares issuable under incentive compensation plans	2,129,000	634,000
Number of shares as adjusted for purposes of computing diluted earnings per common share	620,350,000	304,479,000
Earnings per common share:
Basic (in dollars per share)	$ 0.32	$ 0.69
Diluted (in dollars per share)	$ 0.32	$ 0.69
Stock option awards
Antidilutive securities excluded from computation of earnings per share
Number of shares of common stock excluded from the computation of diluted earnings per share	1,300,000	1,700,000