Stock-Based and Other Compensation Plans (Details 2) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Stock option activity [Rollforward]
Exercised (in shares)	(343,145.000000)	(1,459,490)
Stock Option
Assumptions used to value stock option awards [Abstract]
Expected term (in years)	6 years	5 years 10 months 24 days	5 years 8 months
Expected volatility (in hundredths)	32.60%	35.10%	36.40%
Risk-free rate (in hundredths)	1.40%	1.80%	1.10%
Expected dividend yield (in hundredths)	1.20%	1.10%	1.20%
Weighted-average grant-date fair value of options granted (in dollars per share)	$ 13.93	$ 20.31	$ 17.08
Stock option activity [Rollforward]
Outstanding, beginning balance (in shares)	13,008,322
Granted (in shares)	2,714,185
Exercised (in shares)	(343,145)
Forfeited (in shares)	(808,350)
Outstanding, ending balance (in shares)	14,571,012	13,008,322
Exercisable (in shares)	10,659,799
Stock option activity, additional disclosures [Abstract]
Weighted average exercise price per share outstanding, beginning balance (in dollars per share)	$ 43.98
Weighted average exercise price per share granted (in dollars per share)	47.25
Weighted average exercise price per share exercised (in dollars per share)	23.35
Weighted average exercise price per share forfeited (in dollars per share)	52.24
Weighted average exercise price per share outstanding, ending balance (in dollars per share)	44.59	$ 43.98
Weighted average exercise price per exercisable share (in dollars per share)	$ 41.53
Weighted average remaining contractual term of shares outstanding (in years)	5 years 7 months 6 days
Aggregate intrinsic value of shares outstanding	$ 21
Weighted average remaining contractual term, exercisable shares (in years)	4 years 6 months
Aggregate intrinsic value, exercisable shares	$ 21
Employee Service Share-based Compensation, Aggregate Disclosures [Abstract]
Minimum term to maturity on US Treasuries used to determine the risk free rate assumption in valuing stock options	5 years
Maximum term to maturity on US Treasuries used to determine the risk free rate assumption in valuing stock options	7 years
The period ended, prior to the date of grant, over which an average of daily stock prices is computed in determining the dividend yield	3 years
Duration of dividends	1 year
Total intrinsic value of options exercised	$ 7	$ 58	$ 64
Unrecognized compensation cost related to nonvested awards	$ 34
The weighted-average period over which unrecognized compensation cost is to be recognized (in years)	1 year 3 months 18 days
Restricted Stock
Assumptions used to value stock option awards [Abstract]
Expected volatility (in hundredths)	30.00%	30.00%
Risk-free rate (in hundredths)	0.80%	0.70%
Restricted stock awards, shares subject to service conditions, additional disclosures [Abstract]
Weighted average award date fair value, shares awarded (in dollars per share)	$ 35.53	$ 41.22	$ 38.07
Employee Service Share-based Compensation, Aggregate Disclosures [Abstract]
The period ended, prior to the date of grant, over which an average of daily stock prices is computed in determining the dividend yield	3 years
Unrecognized compensation cost related to nonvested awards	$ 42
The weighted-average period over which unrecognized compensation cost is to be recognized (in years)	1 year 8 months 12 days
Weighted average award date fair value, shares awarded (in dollars per share)	$ 35.53	$ 41.22	$ 38.07
Total fair value of vested restricted stock	$ 62	$ 50	$ 43
Stock Option And Restricted Stock Plan 1992
Employee Service Share-based Compensation, Aggregate Disclosures [Abstract]
Maximum number of shares of common stock authorized for issuance After April 26, 2011 (in shares)	77,400,000
Number of shares of common stock reserved for issuance (in shares)	35,850,503
Shares of common stock available for future grants and awards (in shares)	16,019,550
Expiration period (in years)	10 years
Stock option vesting period	3 years
Percentage of restricted stock awards that time-vest one year from date of grant (in hundredths)	20.00%
Additional percentage of restricted stock awards that time-vest two years from date of grant (in hundredths)	30.00%
Remaining percentage of restricted stock awards that time-vest three years from date of grant (in hundredths)	50.00%
2015 Stock Plan for Non-Employee Directors
Employee Service Share-based Compensation, Aggregate Disclosures [Abstract]
Maximum number of shares of common stock authorized for issuance After April 26, 2011 (in shares)	708,996
Number of shares of common stock reserved for issuance (in shares)	705,615
Shares of common stock available for future grants and awards (in shares)	693,665
Stock Plan for Non-Employee Directors 2005
Employee Service Share-based Compensation, Aggregate Disclosures [Abstract]
Maximum number of shares of common stock authorized for issuance After April 26, 2011 (in shares)	1,600,000
Number of shares of common stock reserved for issuance (in shares)	469,597
Expiration period (in years)	10 years
Stock option vesting period	1 year
The maximum number of stock options authorized for annual and discretionary grants per non-employee director (in shares)	22,400
The number of stock options authorized for annual grants per non-employee director (in shares)	2,800
The maximum number of shares of restricted stock authorized for annual and discretionary grants per non-employee director (in shares)	9,600
The number of shares of restricted stock authorized for annual grants per non-employee director (in shares)	1,200
Stock Plan For Nonemployee Directors 2005, Prior to March 17, 2011
Employee Service Share-based Compensation, Aggregate Disclosures [Abstract]
The maximum number of stock options authorized for annual and discretionary grants per non-employee director (in shares)	11,200
The maximum number of shares of restricted stock authorized for annual and discretionary grants per non-employee director (in shares)	4,800
Nonqualified Stock Option Plan for Non-Employee Directors 1988
Employee Service Share-based Compensation, Aggregate Disclosures [Abstract]
Shares of common stock available for future grants and awards (in shares)	0
Expiration period (in years)	10 years
Stock option vesting period	1 year
The number of stock options authorized for annual grants per non-employee director (in shares)	10,000
The number of stock options granted during the first calendar year of service (in shares)	20,000
Subject to Time Vesting | Restricted Stock
Restricted Stock Awards Activity [Roll Forward]
Outstanding, beginning balance (in shares)	1,048,800
Awarded (in shares)	1,554,002
Vested (in shares)	(1,464,374)
Forfeited (in shares)	(118,958)
Outstanding, ending balance (in shares)	1,019,470	1,048,800
Restricted stock awards, shares subject to service conditions, additional disclosures [Abstract]
Weighted average award date fair value, beginning of period (in dollars per share)	$ 55.68
Weighted average award date fair value, shares awarded (in dollars per share)	39.57
Weighted average award date fair value, shares vested (in dollars per share)	46.57
Weighted average award date fair value, shares forfeited (in dollars per share)	51.36
Weighted average award date fair value, end of period (in dollars per share)	45.55	$ 55.68
Employee Service Share-based Compensation, Aggregate Disclosures [Abstract]
Weighted average award date fair value, shares awarded (in dollars per share)	$ 39.57
Subject to Market Conditions | Restricted Stock
Restricted Stock Awards Activity [Roll Forward]
Outstanding, beginning balance (in shares)	1,518,336
Awarded (in shares)	762,786
Vested (in shares)	(1,172)
Forfeited (in shares)	(350,028)
Outstanding, ending balance (in shares)	1,929,922	1,518,336
Restricted stock awards, shares subject to service conditions, additional disclosures [Abstract]
Weighted average award date fair value, beginning of period (in dollars per share)	$ 29.10
Weighted average award date fair value, shares awarded (in dollars per share)	27.30
Weighted average award date fair value, shares vested (in dollars per share)	42.21
Weighted average award date fair value, shares forfeited (in dollars per share)	28.41
Weighted average award date fair value, end of period (in dollars per share)	28.50	$ 29.10
Employee Service Share-based Compensation, Aggregate Disclosures [Abstract]
Weighted average award date fair value, shares awarded (in dollars per share)	$ 27.30
Second Vesting Option | Stock Option And Restricted Stock Plan 1992
Employee Service Share-based Compensation, Aggregate Disclosures [Abstract]
Stock option vesting period	2 years
Percentage of restricted stock awards that time-vest one year from date of grant (in hundredths)	40.00%
Additional percentage of restricted stock awards that time-vest two years from date of grant (in hundredths)	60.00%