Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Estimated annual effective tax rate (as a percent)	29.50%	29.50%	28.50%
Income Tax
Prior year tax adjustment	$ 55
IRS settlement benefit	(33)
Settlement benefit, previously unrecognized tax benefits	(16)
Settlement benefit, interest	(17)
Benefit from research and development tax credit retroactively extended		(87)
Length of time tax year subject to examination, minimum	3 years
Length of time tax years subject to examination, maximum	8 years
2012
Income Tax
Prior year tax adjustment	28
2013
Income Tax
Prior year tax adjustment	$ 27