Consolidated Statements of Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues
Premiums	$ 78,860.1	$ 73,385.1	$ 68,389.8
Administrative fees	5,298.8	4,976.6	4,590.6
Other revenue	35.1	43.1	41.3
Total operating revenue	84,194.0	78,404.8	73,021.7
Net investment income	779.5	677.6	724.4
Net realized gains on financial instruments	4.9	157.5	177.0
Other than temporary impairment losses on investments:
Total other-than-temporary impairment losses on investments	(147.1)	(99.9)	(56.2)
Portion of other-than-temporary impairment losses recognized in other comprehensive income	31.7	16.5	7.2
Other-than-temporary impairment losses recognized in income	(115.4)	(83.4)	(49.0)
Total revenues	84,863.0	79,156.5	73,874.1
Expenses
Benefit expense	66,834.4	61,116.9	56,854.9
Selling, general and administrative expense:
Selling expense	1,391.5	1,441.1	1,490.1
General and administrative expense	11,166.4	11,093.7	10,258.3
Total selling, general and administrative expense	12,557.9	12,534.8	11,748.4
Interest expense	723.0	653.0	600.7
Amortization of other intangible assets	192.3	230.1	220.9
(Gain) loss on extinguishment of debt	0.0	(9.3)	81.1
Total expenses	80,307.6	74,525.5	69,506.0
Income from continuing operations before income tax expense	4,555.4	4,631.0	4,368.1
Income tax expense	2,085.6	2,071.0	1,808.0
Income from continuing operations	2,469.8	2,560.0	2,560.1
Income from discontinued operations, net of tax	0.0	0.0	9.6
Net income	$ 2,469.8	$ 2,560.0	$ 2,569.7
Basic net income per share:
Basic - continuing operations (in dollars per share)	$ 9.39	$ 9.73	$ 9.28
Basic - discontinued operations (in dollars per share)	0.00	0.00	0.03
Basic net income per share	9.39	9.73	9.31
Diluted net income per share:
Diluted - continuing operations (in dollars per share)	9.21	9.38	8.96
Diluted - discontinued operations (in dollars per share)	0.00	0.00	0.03
Diluted net income per share	9.21	9.38	8.99
Dividends per share	$ 2.60	$ 2.50	$ 1.75