Consolidated Statements Of Income (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Revenues
Premiums	$ 14,138.5	$ 13,684.1
Administrative fees	995.8	962.0
Other revenue	15.9	8.7
Total operating revenue	15,150.2	14,654.8
Net investment income	169.0	184.8
Net realized gains on investments	106.9	57.1
Other-than-temporary impairment losses on investments:
Total other-than-temporary impairment losses on investments	(13.7)	(4.8)
Portion of other-than-temporary impairment losses recognized in other comprehensive income	2.8	2.4
Other-than-temporary impairment losses recognized in income	(10.9)	(2.4)
Total revenues	15,415.2	14,894.3
Expenses
Benefit expense	11,771.9	11,228.0
Selling, general and administrative expense:
Selling expense	393.3	397.0
General and administrative expense	1,772.4	1,679.5
Total selling, general and administrative expense	2,165.7	2,076.5
Interest expense	109.1	105.9
Amortization of other intangible assets	58.7	56.8
Total expenses	14,105.4	13,467.2
Income before income tax expense	1,309.8	1,427.1
Income tax expense	453.3	500.5
Net income	$ 856.5	$ 926.6
Net income per share
Basic	$ 2.56	$ 2.48
Diluted	$ 2.53	$ 2.44
Dividends per share	$ 0.2875	$ 0.25