Acquisitions and Dispositions (Details) $ / shares in Units, $ in Millions	3 Months Ended		12 Months Ended
	Dec. 31, 2015 USD ($) $ / shares	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($) $ / shares	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Feb. 24, 2016 $ / shares
Acquisitions and Dispositions [Abstract]
Cash consideration for each share of Company stock | $ / shares	$ 103.40		$ 103.40
Shares of acquirer common stock for each share of Company stock	0.5152		0.5152
Closing price of Anthem common stock | $ / shares						$ 130.75
Reverse termination fee payable to Company	$ 1,850		$ 1,850
Merger-related transaction costs			66
Acquisitions-related costs, after-tax	$ 28	$ 29	$ 57
Other acquisitions and dispositions, results