Earnings Per Common Share (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Numerator (basic and diluted):
Income from continuing operations	$ 109	$ 61
Less: Allocation to unvested restricted stock awards	1	1
Income from continuing operations attributable to common shareholders	108	60
Income from discontinued operations, net	0	3
Less: Allocation to unvested restricted stock awards	0	0
Income (loss) from discontinued operations attributable to common shareholders	0	3
Net income available to common shareholders	$ 108	$ 63
Denominator:
Basic common shares (based upon weighted average) (in shares)	330	344
Add: Stock option dilution (in shares)	3	3
Diluted common shares (in shares)	333	347