Stock Plans (Narrative) (Details) $ / shares in Units, $ in Millions	1 Months Ended	9 Months Ended
	Feb. 25, 2015 shares	Sep. 30, 2015 USD ($) ShareBasedCompensationPlan $ / shares shares	Sep. 30, 2014 USD ($) $ / shares shares	Dec. 31, 2014 USD ($) $ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of stock-based compensation plan under which grants were made | ShareBasedCompensationPlan		6
Number of stock-based compensation plan under which grants were not made | ShareBasedCompensationPlan		4
Shares authorized for grant under the plans (in shares) | shares		22,541,000
Shares available for grant under the plan (in shares) | shares		12,629,000
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expense recognized during the period		$ 6	$ 3
Shares granted (in shares) | shares	665,000	738,000
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expense recognized during the period		$ 13	$ 12
Shares granted (in shares) | shares		2,814,000	3,836,000
Restricted Stock
Restricted stock granted		$ 13	$ 25
Restricted stock vested		15	15
Fair value of unvested restricted stock		$ 34	$ 48	$ 52
Restriced stock, grant date fair value per share | $ / shares		$ 5.93	$ 4.74	$ 4.75
Remaining unrecognized compensation cost associated with unvested restricted stock awards		$ 29
Weighted average period over which unvested restricted stock awards unrecognized compensation cost is expected to be recognized (in years)		1 year 6 months