Additional Shareholders' Equity Information (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Common stock shares issued [Rollforward]
Shares, beginning of period (in shares)	196,656,846	195,440,048
Exercise of common stock options (in shares)	1,265,231	837,096
Restricted stock awards, net of forfeitures (in shares)	426,665	379,702
Shares, end of period (in shares)	198,348,742	196,656,846	195,440,048
Treasury stock [Rollforward]
Shares, beginning of period (in shares)	18,736,520	18,650,064
Shares received from employees in payment of withholding taxes due on vesting of shares of restricted stock (in shares)	141,124	186,556
Rabbi Trust Shares Distributed and/or Sold (in shares)	(102,268)	(100,100)
Shares, end of period (in shares)	18,775,376	18,736,520	18,650,064
Components And Changes In Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	$ (100)	$ (104)	$ (75)
Realized Amounts Reclassified Into Earnings	7	5	16
Net Change in Other			(45)
Unrealized Change in Fair Value	(20)	(1)
End Balance	(113)	(100)	(104)
Effective income tax rate applied to AOCI (in hundredths)	35.00%	35.00%	35.00%
Oil and gas cash flow hedges [Member]
Components And Changes In Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	0	0	(12)
Realized Amounts Reclassified Into Earnings	0	0	12
Net Change in Other			0
Unrealized Change in Fair Value	0	0
End Balance	0	0	0
Interest rate cash flow hedges [Member]
Components And Changes In Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	(26)	(42)	(2)
Realized Amounts Reclassified Into Earnings	1	1	1
Net Change in Other			(41)
Unrealized Change in Fair Value	0	15
End Balance	(25)	(26)	(42)
Pension-related and other [Member]
Components And Changes In Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	(74)	(62)	(61)
Realized Amounts Reclassified Into Earnings	6	4	3
Net Change in Other			(4)
Unrealized Change in Fair Value	(20)	(16)
End Balance	$ (88)	$ (74)	$ (62)