Earnings Per Share (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Earnings Per Share [Abstract]
Antidilutive securities excluded (in shares)	1,200,000	1,300,000
Numerator:
Net income	$ 21	$ 13
Net income available to common stockholders	21	13
Denominator:
Denominator for basic earnings per share—weighted-average common shares (in shares)	93,310,000	63,131,000
Denominator for diluted earnings per share—adjusted weighted-average common shares (in shares)	106,380,000	76,266,000
Basic earnings per share (in dollars per share)	$ 0.22	$ 0.21
Diluted earnings per share (in dollars per share)	$ 0.19	$ 0.17
Convertible debt interest - 1 7/8 percent notes [Member]
Numerator:
Convertible debt interest—1 7/8 percent notes	$ 0	$ 0
Denominator:
Convertible subordinated notes (in shares)	0	1,015,000
Employee stock options and warrants [Member]
Denominator:
Incremental common shares attributable to share-based payment arrangements (in shares)	619,000	709,000
Convertible subordinated notes - 4 percent [Member]
Denominator:
Convertible subordinated notes (in shares)	11,866,000	10,794,000
Restricted stock units [Member]
Denominator:
Incremental common shares attributable to share-based payment arrangements (in shares)	585,000	617,000