Stock Plans (Narrative) (Details) $ / shares in Units, $ in Millions		2 Months Ended	9 Months Ended	12 Months Ended
	Feb. 25, 2015 shares	Feb. 17, 2014 shares	Sep. 30, 2013	Dec. 31, 2015 USD ($) ShareBasedCompensationPlan entity $ / shares shares	Dec. 31, 2014 USD ($) $ / shares shares	Dec. 31, 2013 USD ($) $ / shares shares	Dec. 31, 2012 USD ($) $ / shares 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)				22,541,000
Shares available for grant under the plan (in shares)				12,475,000
Unrecognized compensation cost | $				$ 0
Non Employee Directors Compensation Plans
Exercisable at end of period (in shares)				50,000	83,000	83,000
Exercisable at end of period (in dollars per share) | $ / shares				$ 13.40	$ 13.23	$ 13.23
Deferred Fee Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized for grant under the plans (in shares)				541,000
EIP Plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized for grant under the plans (in shares)				20,000,000
Shares available for grant under the plan (in shares)				11,998,000
Shares granted (in shares)				0
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized for grant under the plans (in shares)						1,124,000
Expense recognized during the period | $				$ 7	$ 4	$ 1
Shares granted (in shares)	665,000	1,028,000		738,000	1,037,000	1,124,000	979,000
Performance Shares
Initial period over which target number of performance shares are awarded				90 days
Measurement period				3 years
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expense recognized during the period | $				$ 20	$ 16	$ 14
Shares granted (in shares)				2,815,000	4,314,000	3,360,000
Restricted Stock
Restricted stock granted | $				$ 13	$ 29	$ 16
Restricted stock vested | $				15	16	14
Fair value of unvested restricted stock | $				$ 33	$ 52	$ 29	$ 30
Restriced stock, grant date fair value per share | $ / shares				$ 5.93	$ 4.75	$ 4.80	$ 6.08
Remaining unrecognized compensation cost associated with unvested restricted stock awards | $				$ 24
Weighted average period over which unvested restricted stock awards unrecognized compensation cost is expected to be recognized (in years)				1 year 2 months 12 days
Non-Employee Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized for grant under the plans (in shares)				2,541,000
Shares available for grant under the plan (in shares)				477,000
Expense recognized during the period | $				$ (1)	$ 4	$ 2
Non Employee Directors Compensation Plans
Plan units earned during the period (in shares)				334,188	237,607	374,383
Number of directors participating in the plan during the period | entity				10
Cash value of the fees payable to the director as a percentage of closing prices of common stock (in hundredths)			85.00%
Cash compensation | $				$ 1	$ 1	$ 1
Exercisable at end of period (in shares)				40,000
Exercisable at end of period (in dollars per share) | $ / shares				$ 10.37