Consolidated Statements of Income (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues
Premiums	$ 68,389.8	$ 66,119.1	$ 56,496.7
Administrative fees	4,590.6	4,031.9	3,934.1
Other revenue	41.3	40.4	83.2
Total operating revenue	73,021.7	70,191.4	60,514.0
Net investment income	724.4	659.1	686.1
Net realized gains on investments	177.0	271.9	334.9
Other than temporary impairment losses on investments:
Total other-than-temporary impairment losses on investments	(56.2)	(100.6)	(41.2)
Portion of other-than-temporary impairment losses recognized in other comprehensive income	7.2	1.7	3.4
Other-than-temporary impairment losses recognized in income	(49.0)	(98.9)	(37.8)
Total revenues	73,874.1	71,023.5	61,497.2
Expenses
Benefit expense	56,854.9	56,237.1	48,213.6
Selling, general and administrative expense:
Selling expense	1,490.1	1,526.9	1,586.9
General and administrative expense	10,258.3	8,426.0	7,093.6
Total selling, general and administrative expense	11,748.4	9,952.9	8,680.5
Interest expense	600.7	602.7	511.8
Amortization of other intangible assets	220.9	245.3	233.0
Loss on extinguishment of debt	81.1	145.3	0
Total expenses	69,506.0	67,183.3	57,638.9
Income from continuing operations before income tax expense	4,368.1	3,840.2	3,858.3
Income tax expense	1,808.0	1,205.9	1,207.3
Income from continuing operations	2,560.1	2,634.3	2,651.0
Income (loss) from discontinued operations, net of tax	9.6	(144.6)	4.5
Net income	$ 2,569.7	$ 2,489.7	$ 2,655.5
Basic net income (loss) per share:
Basic - continuing operations (in dollars per share)	$ 9.28	$ 8.83	$ 8.25
Basic - discontinued operations (in dollars per share)	$ 0.03	$ (0.49)	$ 0.01
Basic net income per share	$ 9.31	$ 8.34	$ 8.26
Diluted net income (loss) per share:
Diluted - continuing operations (in dollars per share)	$ 8.96	$ 8.67	$ 8.17
Diluted - discontinued operations (in dollars per share)	$ 0.03	$ (0.47)	$ 0.01
Diluted net income per share	$ 8.99	$ 8.20	$ 8.18
Dividends per share	$ 1.75	$ 1.50	$ 1.15