Schedule II-Condensed Financial Information Of Registrant (Balance Sheets) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 2,113.5	$ 2,151.7	$ 1,582.1
Fixed maturity securities (amortized cost of $889.6 and $1,798.8)	16,920.0	17,467.4
Equity securities (cost of $53.0 and $148.7)	1,441.8	1,906.6
Other invested assets, current	19.1	20.2
Other receivables	2,421.4	2,117.0
Income taxes receivable	316.6	308.9
Securities lending collateral	1,300.4	1,515.2
Other current assets	1,555.7	1,473.9
Total current assets	30,862.1	31,947.8
Equity securities (cost of $6.5 and $6.6)	31.0	31.5
Other invested assets, long-term	2,041.1	1,695.9
Property and equipment, net	2,019.8	1,944.3
Other noncurrent assets	485.4	512.3
Total assets	61,717.8	61,676.3
Current liabilities:
Accounts payable and accrued expenses	3,318.8	3,651.8
Security trades pending payable	73.1	66.2
Securities lending payable	1,300.9	1,515.3
Current portion of long-term debt	0.0	624.3
Other current liabilities	2,816.1	1,861.2
Total current liabilities	19,092.6	18,752.7
Long-term debt, less current portion	15,324.5	14,019.6
Other noncurrent liabilities	994.3	1,035.8
Total liabilities	$ 38,673.7	$ 37,425.0
Commitments and contingencies-Note 5
Shareholders' equity
Preferred stock, without par value, shares authorized - 100,000,000; shares issued and outstanding - none	$ 0.0	$ 0.0
Common stock, par value $0.01, shares authorized - 900,000,000; shares issued and outstanding - 261,238,188 and 268,109,932	2.6	2.7
Additional paid-in capital	8,555.6	10,062.3
Retained earnings	14,778.5	14,014.4
Accumulated other comprehensive (loss) income	(292.6)	171.9
Total shareholders' equity	23,044.1	24,251.3	24,765.2	$ 23,802.7
Total liabilities and shareholders' equity	61,717.8	61,676.3
Anthem, Inc. [Member]
Current assets:
Cash and cash equivalents	492.3	739.8	$ 1,174.5	$ 588.1
Fixed maturity securities (amortized cost of $889.6 and $1,798.8)	794.0	1,753.4
Equity securities (cost of $53.0 and $148.7)	82.0	206.7
Other invested assets, current	5.9	5.7
Other receivables	77.0	44.6
Income taxes receivable	236.5	227.9
Net due from subsidiaries	0.0	327.3
Securities lending collateral	130.6	224.8
Other current assets	394.0	232.5
Total current assets	2,212.3	3,762.7
Equity securities (cost of $6.5 and $6.6)	6.5	6.6
Other invested assets, long-term	630.1	654.5
Property and equipment, net	116.8	134.0
Deferred tax assets, net	146.6	0.0
Investment in subsidiaries	36,524.4	35,647.2
Other noncurrent assets	129.8	113.0
Total assets	39,766.5	40,318.0
Current liabilities:
Accounts payable and accrued expenses	615.5	599.9
Security trades pending payable	13.4	14.0
Securities lending payable	130.6	224.8
Net due to subsidiaries	93.2	0.0
Current portion of long-term debt	0.0	624.3
Other current liabilities	278.1	280.1
Total current liabilities	1,130.8	1,743.1
Long-term debt, less current portion	15,299.6	13,994.7
Deferred tax liabilities, net	0.0	15.2
Other noncurrent liabilities	292.0	313.7
Total liabilities	$ 16,722.4	$ 16,066.7
Commitments and contingencies-Note 5
Shareholders' equity
Preferred stock, without par value, shares authorized - 100,000,000; shares issued and outstanding - none	$ 0.0	$ 0.0
Common stock, par value $0.01, shares authorized - 900,000,000; shares issued and outstanding - 261,238,188 and 268,109,932	2.6	2.7
Additional paid-in capital	8,555.6	10,062.3
Retained earnings	14,778.5	14,014.4
Accumulated other comprehensive (loss) income	(292.6)	171.9
Total shareholders' equity	23,044.1	24,251.3
Total liabilities and shareholders' equity	$ 39,766.5	$ 40,318.0