Mergers and Acquistions (Details) $ / shares in Units, $ in Millions	3 Months Ended						12 Months Ended
	Dec. 31, 2016 USD ($) $ / shares	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Dec. 31, 2016 USD ($) $ / shares	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Feb. 22, 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										$ 163.27
Merger-related costs, before tax							$ 166	$ 66
Merger-related costs, after-tax	$ 39	$ 46	$ 26	$ 36	$ 28	$ 29	147	57
Other acquisitions and dispositions, results
Merger agreement not consummated [Member]
Gain Contingencies [Line Items]
Gain Contingency, Description							The Company incurred pre-tax costs of $166 million ($147 million after-tax) for the year ended December 31, 2016, and $66 million ($57 million after-tax) for the year ended December 31, 2015 directly related to the proposed merger. These costs consisted primarily of fees for financial advisory, legal and other professional services. If the merger is consummated, most of the merger-related costs are not deductible for federal income tax purposes. If the merger is not consummated, most of these costs would become deductible for federal income tax purposes, resulting in a tax benefit of approximately $50 million.
Tax benefit if merger is not consummated	$ 50						$ 50