Additional Shareholders' Equity Information (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Common stock shares issued [Rollforward]
Shares, beginning of period (in shares)	399,841,717	396,697,484
Exercise of common stock options (in shares)	1,459,490	1,892,962
Restricted stock awards, net of forfeitures (in shares)	1,028,118	1,251,271
Shares, end of period (in shares)	402,329,325	399,841,717	396,697,484
Treasury stock [Rollforward]
Shares, beginning of period (in shares)	37,600,051	37,550,752
Shares received from employees in payment of withholding taxes due on vesting of shares of restricted stock (in shares)	254,888	250,307
Rabbi Trust Shares Distributed and/or Sold (in shares)	(219,049)	(201,008)
Shares, end of period (in shares)	37,635,890	37,600,051	37,550,752
Components And Changes In Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	$ (117)	$ (113)	$ (100)
Realized Amounts Reclassified Into Earnings	12	13	7
Unrealized Change in Fair Value	15	(17)	(20)
End Balance	(90)	(117)	(113)
Effective income tax rate applied to AOCI (in hundredths)	35.00%	35.00%	35.00%
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(23)
Interest rate cash flow hedges [Member]
Components And Changes In Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	(24)	(25)	(26)
Realized Amounts Reclassified Into Earnings	1	1	1
Unrealized Change in Fair Value	0	0	0
End Balance	(23)	(24)	(25)
Pension-related and other [Member]
Components And Changes In Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	(93)	(88)	(74)
Realized Amounts Reclassified Into Earnings	11	12	6
Unrealized Change in Fair Value	15	(17)	(20)
End Balance	$ (67)	$ (93)	$ (88)