Stock-Based Compensation (Details 3) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Additional disclosures
Weighted average remaining vesting period	3 years	2 years
Stock Options
Stock Options
Vesting period	5 years
Expiration period	10 years
Shares
Outstanding at the beginning of the period (in shares)	24,000,000	30,000,000
Granted (in shares)	332,750	1,000,000
Exercised (in shares)	1,000,000	2,000,000
Forfeited (in shares)	121,850
Outstanding at the end of the period (in shares)	23,000,000	29,000,000
Option shares vested and expected to vest at the end of the period	23,000,000	29,000,000
Option shares exercisable at the end of the period	20,000,000	23,000,000
Weighted average exercise price
Outstanding at the beginning of the period (in dollars per share)	$ 22	$ 21
Granted (in dollars per share)	$ 22	$ 20
Exercised (in dollars per share)	$ 16	$ 11
Forfeited (in dollars per share)	$ 27	$ 19
Outstanding at the end of the period (in dollars per share)	$ 22	$ 22
Option shares vested and expected to vest at the end of the period (in dollars per share)	$ 22	$ 22
Option shares exercisable at the end of the period (in dollars per share)	$ 23	$ 24
Aggregate intrinsic value
Exercised	$ 10	$ 17
Option shares vested and expected to vest at the end of the period	93	82
Option shares exercisable at the end of the period	72	45
Weighted average remaining option term
Outstanding at the end of the period	4 years	4 years
Option shares vested and expected to vest at the end of the period	4 years	4 years
Option shares exercisable at the end of the period	3 years	4 years
Additional disclosures
Total unrecognized compensation expense	$ 11	$ 17