Consolidated Statements of Shareholders' Equity (USD $) In Millions, unless otherwise specified	Total	Common Stock [Member]	Additional Paid In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]
Balance at Dec. 31, 2010	$ 23,812.6	$ 3.8	$ 12,862.6	$ 10,721.6	$ 224.6
Balance (in shares) at Dec. 31, 2010		377.7
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	2,646.7			2,646.7
Other comprehensive income (loss)	(109.7)				(109.7)
Repurchase and retirement of common stock	(3,039.8)	(0.4)	(1,523.2)	(1,516.2)
Repurchase and retirement of common stock, shares		(44.5)
Dividends and dividend equivalents	(361.4)			(361.4)
Issuance of common stock under employee stock plans, net of related tax benefits	339.8		339.8
Issuance of common stock under employee stock plans, net of related tax benefits (in shares)		6.2
Balance at Dec. 31, 2011	23,288.2	3.4	11,679.2	11,490.7	114.9
Balance (in shares) at Dec. 31, 2011		339.4
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	2,655.5			2,655.5
Other comprehensive income (loss)	184.2				184.2
Repurchase and retirement of common stock	(2,496.8)	(0.4)	(1,368.5)	(1,127.9)
Repurchase and retirement of common stock, shares	(39.7)	(39.7)
Dividends and dividend equivalents	(371.2)			(371.2)
Issuance of convertible debentures	331.5		331.5
Conversion of stock awards in connection with AMERIGROUP Corporation acquisition	19.7		19.7
Issuance of common stock under employee stock plans, net of related tax benefits	191.6		191.6
Issuance of common stock under employee stock plans, net of related tax benefits (in shares)		5.0
Balance at Dec. 31, 2012	23,802.7	3.0	10,853.5	12,647.1	299.1
Balance (in shares) at Dec. 31, 2012		304.7
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	2,489.7			2,489.7
Other comprehensive income (loss)	(115.9)				(115.9)
Premiums paid on equity options	(7.9)		(7.9)
Repurchase and retirement of common stock	(1,620.1)	(0.1)	(749.5)	(870.5)
Repurchase and retirement of common stock, shares	(20.7)	(20.7)
Convertible debentures tax adjustment	(3.3)		(3.3)
Dividends and dividend equivalents	(452.4)			(452.4)
Issuance of common stock under employee stock plans, net of related tax benefits	672.4		672.4
Issuance of common stock under employee stock plans, net of related tax benefits (in shares)		9.3
Balance at Dec. 31, 2013	$ 24,765.2	$ 2.9	$ 10,765.2	$ 13,813.9	$ 183.2
Balance (in shares) at Dec. 31, 2013		293.3