Schedule II-Condensed Financial Information Of Registrant (Balance Sheets (Parenthetical)) (Details) - USD ($) $ / shares in Units, $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Available-for-sale fixed maturity securities investments, current, amortized cost	$ 16,991.8	$ 16,950.0
Available-for-sale equity securities investments, current, cost	1,076.1	1,055.8
Available-for-sale fixed maturity securities investments, long-term, amortized cost	524.6	550.4
Available-for-sale equity securities investments, long-term, cost	$ 27.2	$ 27.3
Preferred stock, par value	$ 0	$ 0
Preferred stock, shares authorized	100,000,000	100,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	900,000,000	900,000,000
Common stock, shares issued	263,747,395	261,238,188
Common stock, shares outstanding	263,747,395	261,238,188
Anthem, Inc. [Member]
Available-for-sale fixed maturity securities investments, current, amortized cost	$ 463.4	$ 889.6
Available-for-sale equity securities investments, current, cost	35.7	53.0
Available-for-sale equity securities investments, long-term, cost	$ 6.4	$ 6.5
Preferred stock, par value	$ 0	$ 0
Preferred stock, shares authorized	100,000,000	100,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	900,000,000	900,000,000
Common stock, shares issued	263,747,395	261,238,188
Common stock, shares outstanding	263,747,395	261,238,188