Stock-Based Compensation (Narrative) (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended			1 Months Ended		12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Jan. 31, 2013 Performance Share Units	Jan. 31, 2012 Performance Share Units	Dec. 31, 2013 Performance Share Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum shares available for grants	4,000,000
Share-based compensation expense	$ 20	$ 22	$ 13
Employee service share-based compensation, tax benefit from compensation expense	8	8	5
Amounts paid to settle share units	11	11	4
Compensation cost not yet recognized	$ 20
Expected weighted average recognition period for share-based compensation expense, in months	20 months
Performance period						3 years
Percentage of shares issued per share unit, minimum						0.00%
Percentage of shares issued per share unit, maximum						200.00%
Fair value of each share unit, per share				$ 31.19	$ 35.68	$ 31.19	[1]
Closing common share price				$ 30.72	$ 33.13
Three-year risk-free rate				0.36%	0.41%
Volatility rate, minimum				12.00%	17.00%
Volatility rate, maximum				21.00%	31.00%

[1] Includes performance share units (share units) granted to certain executive and nonexecutive officers and other eligible employees in 2013 under the 2006 Plan.