Stock Plans (Restricted Shares Outstanding) (Details) - Restricted Stock [Member] - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Balance at beginning of period (in shares)	7,048	7,807	6,234
Shares granted (in shares)	5,936	2,815	4,314
Shares vested (in shares)	(3,720)	(3,215)	(2,372)
Shares forfeited (in shares)	(908)	(359)	(369)
Balance at end of period (in shares)	8,356	7,048	7,807
Balance at beginning of period (in dollars per shares)	$ 5.93	$ 4.75	$ 4.80
Restricted stock granted (in dollars per shares)	4.36	7.92	4.91
Restricted stock vested (in dollars per shares)	5.26	4.89	5.22
Restricted stock forfeited (in dollars per shares)	5.11	5.10	4.55
Balance at end of period (in dollars per shares)	$ 5.20	$ 5.93	$ 4.75
Balance at beginning of period	$ 33	$ 52	$ 29
Restricted stock granted	20	13	29
Restricted stock vested	13	15	16
Balance at end of period	$ 28	$ 33	$ 52