Stock-Based Compensation (Details 3) (USD $) In Millions, except Share data, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Additional disclosures
Weighted average remaining vesting period	2 years	2 years
Stock Options
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)	2,000,000	3,000,000
Forfeited (in shares)	3,640,670	1,000,000
Outstanding at the end of the period (in shares)	19,000,000	27,000,000
Option shares vested and expected to vest at the end of the period	19,000,000	27,000,000
Option shares exercisable at the end of the period	16,000,000	22,000,000
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	$ 12
Forfeited (in dollars per share)	$ 28	$ 23
Outstanding at the end of the period (in dollars per share)	$ 21	$ 22
Option shares vested and expected to vest at the end of the period (in dollars per share)	$ 21	$ 22
Option shares exercisable at the end of the period (in dollars per share)	$ 22	$ 24
Aggregate intrinsic value
Exercised	$ 17	$ 22
Option shares vested and expected to vest at the end of the period	102	91
Option shares exercisable at the end of the period	80	51
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	3 years
Additional disclosures
Total unrecognized compensation expense	$ 7	$ 10