Share-Based Compensation Plans Schedule of Performance-based plans (Details) (Performance Shares [Member], USD $) In Millions, except Share data in Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Target PSAs granted	816		1,135		1,369
Fair value	$ 81	[1]	$ 58	[1]	$ 47	[1]
Number of shares that would be issued based on current performance levels	816		2,243		2,682
Unamortized expense, based on current performance levels	$ 65		$ 82		$ 34

[1] Represents per share weighted average fair value of award at date of grant.