Medicare Part D Pharmacy Benefits (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Other current receivables	$ 3,624	$ 3,998
Other policy liabilities	5,247	5,279
CMS Subsidies [Member]
Other current receivables	529	881
Other policy liabilities	0	0
Drug Discount [Member]
Other current receivables	184	425
Other policy liabilities	84	152
Risk-Share [Member]
Other current receivables	0	0
Other policy liabilities	$ 103	$ 214