Earnings Per Common Share (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Numerator (basic and diluted):
Income from continuing operations	$ 76	$ 62
Less: Allocation to unvested restricted stock awards	1	1
Income from continuing operations attributable to common shareholders	75	61
Loss from discontinued operations, net	(2)	(9)
Loss from discontinued operations attributable to common shareholders	(2)	(9)
Net income attributable to common shareholders	$ 73	$ 52
Denominator:
Basic common shares (based upon weighted average) (in shares)	351	350
Add:
Stock option dilution (in shares)	3	2
Diluted common shares (in shares)	354	352