Segment Information (Schedule of Segment Reporting Information, By Segment) (Details) (USD $) In Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Revenues - external customers, Premiums	$ 8,849,376	$ 8,376,751	$ 17,615,667	$ 16,538,614
Services revenue	343,509	132,702	678,451	265,722
Total revenues - external customers	9,192,885	8,509,453	18,294,118	16,804,336
Intersegment revenues	0	0	0	0
Investment income	91,246	79,790	180,731	165,245
Total revenues	9,284,131	8,589,243	18,474,849	16,969,581
Operating expenses, Benefits	7,269,768	6,869,096	14,614,522	13,686,478
Operating expenses, Operating costs	1,192,405	1,093,690	2,448,248	2,154,547
Operating expenses, Depreciation and amortization	67,781	64,381	133,890	123,240
Total operating expenses	8,529,954	8,027,167	17,196,660	15,964,265
Income from operations	754,177	562,076	1,278,189	1,005,316
Interest expense	27,663	26,222	54,891	52,536
Income before income taxes	726,514	535,854	1,223,298	952,780
Health and Well-Being Services [Member] | Products [Member]
Intersegment revenues	433,869	306,983	868,509	593,896
Retail [Member] | Products [Member]
Intersegment revenues	0	0	0	0
Employer Group [Member] | Products [Member]
Intersegment revenues	0	0	0	0
Other Businesses [Member] | Products [Member]
Intersegment revenues	0	0	0	0
Products [Member]
Intersegment revenues	0	0	0	0
Products [Member] | Eliminations/Corporate [Member]
Intersegment revenues	(433,869)	(306,983)	(868,509)	(593,896)
Retail [Member]
Revenues - external customers, Premiums	5,392,379	4,813,892	10,701,140	9,572,911
Services revenue	3,894	2,540	6,767	5,341
Total revenues - external customers	5,396,273	4,816,432	10,707,907	9,578,252
Intersegment revenues	0	0	0	0
Investment income	18,949	19,529	37,945	40,737
Total revenues	5,415,222	4,835,961	10,745,852	9,618,989
Operating expenses, Benefits	4,390,146	3,923,278	8,944,389	7,917,327
Operating expenses, Operating costs	490,133	555,035	1,022,545	1,051,741
Operating expenses, Depreciation and amortization	31,875	31,710	58,860	59,201
Total operating expenses	4,912,154	4,510,023	10,025,794	9,028,269
Income from operations	503,068	325,938	720,058	590,720
Interest expense	0	0	0	0
Income before income taxes	503,068	325,938	720,058	590,720
Retail [Member] | Medicare Advantage [Member]
Revenues - external customers, Premiums	4,555,163	4,106,667	9,079,789	8,165,834
Retail [Member] | Medicare Stand-Alone PDP [Member]
Revenues - external customers, Premiums	601,345	504,296	1,158,817	1,007,809
Retail [Member] | Medicare [Member]
Revenues - external customers, Premiums	5,156,508	4,610,963	10,238,606	9,173,643
Retail [Member] | Fully-Insured [Member]
Revenues - external customers, Premiums	206,291	183,261	407,179	362,078
Retail [Member] | Specialty [Member]
Revenues - external customers, Premiums	29,580	19,668	55,355	37,190
Retail [Member] | Military Services [Member]
Revenues - external customers, Premiums	0	0	0	0
Retail [Member] | Medicaid and Other [Member]
Revenues - external customers, Premiums	0	0	0	0
Retail [Member] | Provider [Member]
Services revenue	0	0	0	0
Retail [Member] | ASO and Other [Member]
Services revenue	3,894	2,540	6,767	5,341
Retail [Member] | Pharmacy [Member]
Services revenue	0	0	0	0
Retail [Member] | Services [Member]
Intersegment revenues	0	0	0	0
Employer Group [Member]
Revenues - external customers, Premiums	2,216,340	2,304,548	4,443,152	4,613,646
Services revenue	86,657	100,234	179,203	199,357
Total revenues - external customers	2,302,997	2,404,782	4,622,355	4,813,003
Intersegment revenues	3,317	3,279	6,598	6,668
Investment income	11,793	10,207	23,408	21,247
Total revenues	2,318,107	2,418,268	4,652,361	4,840,918
Operating expenses, Benefits	1,799,711	1,870,910	3,551,115	3,767,841
Operating expenses, Operating costs	386,925	414,505	810,832	843,329
Operating expenses, Depreciation and amortization	23,062	25,097	43,250	48,515
Total operating expenses	2,209,698	2,310,512	4,405,197	4,659,685
Income from operations	108,409	107,756	247,164	181,233
Interest expense	0	0	0	0
Income before income taxes	108,409	107,756	247,164	181,233
Employer Group [Member] | Medicare Advantage [Member]
Revenues - external customers, Premiums	764,595	778,542	1,561,349	1,536,355
Employer Group [Member] | Medicare Stand-Alone PDP [Member]
Revenues - external customers, Premiums	1,911	1,154	3,728	2,290
Employer Group [Member] | Medicare [Member]
Revenues - external customers, Premiums	766,506	779,696	1,565,077	1,538,645
Employer Group [Member] | Fully-Insured [Member]
Revenues - external customers, Premiums	1,216,601	1,300,759	2,415,191	2,628,760
Employer Group [Member] | Specialty [Member]
Revenues - external customers, Premiums	233,233	224,093	462,884	446,241
Employer Group [Member] | Military Services [Member]
Revenues - external customers, Premiums	0	0	0	0
Employer Group [Member] | Medicaid and Other [Member]
Revenues - external customers, Premiums	0	0	0	0
Employer Group [Member] | Provider [Member]
Services revenue	0	0	0	0
Employer Group [Member] | ASO and Other [Member]
Services revenue	86,657	100,234	179,203	199,357
Employer Group [Member] | Pharmacy [Member]
Services revenue	0	0	0	0
Employer Group [Member] | Services [Member]
Intersegment revenues	3,317	3,279	6,598	6,668
Health and Well-Being Services [Member]
Revenues - external customers, Premiums	0	0	0	0
Services revenue	225,013	2,891	442,266	6,054
Total revenues - external customers	225,013	2,891	442,266	6,054
Intersegment revenues	2,507,555	2,230,785	5,063,586	4,425,626
Investment income	0	0	0	0
Total revenues	2,732,568	2,233,676	5,505,852	4,431,680
Operating expenses, Benefits	0	0	0	0
Operating expenses, Operating costs	2,625,168	2,176,392	5,281,450	4,321,088
Operating expenses, Depreciation and amortization	19,597	6,411	40,226	11,492
Total operating expenses	2,644,765	2,182,803	5,321,676	4,332,580
Income from operations	87,803	50,873	184,176	99,100
Interest expense	0	0	0	0
Income before income taxes	87,803	50,873	184,176	99,100
Health and Well-Being Services [Member] | Medicare Advantage [Member]
Revenues - external customers, Premiums	0	0	0	0
Health and Well-Being Services [Member] | Medicare Stand-Alone PDP [Member]
Revenues - external customers, Premiums	0	0	0	0
Health and Well-Being Services [Member] | Medicare [Member]
Revenues - external customers, Premiums	0	0	0	0
Health and Well-Being Services [Member] | Fully-Insured [Member]
Revenues - external customers, Premiums	0	0	0	0
Health and Well-Being Services [Member] | Specialty [Member]
Revenues - external customers, Premiums	0	0	0	0
Health and Well-Being Services [Member] | Military Services [Member]
Revenues - external customers, Premiums	0	0	0	0
Health and Well-Being Services [Member] | Medicaid and Other [Member]
Revenues - external customers, Premiums	0	0	0	0
Health and Well-Being Services [Member] | Provider [Member]
Services revenue	222,401	2,891	437,447	6,054
Health and Well-Being Services [Member] | ASO and Other [Member]
Services revenue	0	0	0	0
Health and Well-Being Services [Member] | Pharmacy [Member]
Services revenue	2,612	0	4,819	0
Health and Well-Being Services [Member] | Services [Member]
Intersegment revenues	2,073,686	1,923,802	4,195,077	3,831,730
Other Businesses [Member]
Revenues - external customers, Premiums	1,240,657	1,258,311	2,471,375	2,352,057
Services revenue	27,945	27,037	50,215	54,970
Total revenues - external customers	1,268,602	1,285,348	2,521,590	2,407,027
Intersegment revenues	0	0	0	0
Investment income	13,371	10,027	25,675	19,881
Total revenues	1,281,973	1,295,375	2,547,265	2,426,908
Operating expenses, Benefits	1,149,320	1,127,876	2,258,759	2,104,482
Operating expenses, Operating costs	110,617	115,248	229,571	230,060
Operating expenses, Depreciation and amortization	2,644	3,129	4,352	6,020
Total operating expenses	1,262,581	1,246,253	2,492,682	2,340,562
Income from operations	19,392	49,122	54,583	86,346
Interest expense	0	0	0	0
Income before income taxes	19,392	49,122	54,583	86,346
Other Businesses [Member] | Medicare Advantage [Member]
Revenues - external customers, Premiums	0	0	0	0
Other Businesses [Member] | Medicare Stand-Alone PDP [Member]
Revenues - external customers, Premiums	77,184	194,772	153,080	269,148
Other Businesses [Member] | Medicare [Member]
Revenues - external customers, Premiums	77,184	194,772	153,080	269,148
Other Businesses [Member] | Fully-Insured [Member]
Revenues - external customers, Premiums	0	0	0	0
Other Businesses [Member] | Specialty [Member]
Revenues - external customers, Premiums	0	0	0	0
Other Businesses [Member] | Military Services [Member]
Revenues - external customers, Premiums	934,738	885,368	1,858,015	1,730,362
Other Businesses [Member] | Medicaid and Other [Member]
Revenues - external customers, Premiums	228,735	178,171	460,280	352,547
Other Businesses [Member] | Provider [Member]
Services revenue	0	0	0	0
Other Businesses [Member] | ASO and Other [Member]
Services revenue	27,945	27,037	50,215	54,970
Other Businesses [Member] | Pharmacy [Member]
Services revenue	0	0	0	0
Other Businesses [Member] | Services [Member]
Intersegment revenues	0	0	0	0
Eliminations/Corporate [Member]
Revenues - external customers, Premiums	0	0	0	0
Services revenue	0	0	0	0
Total revenues - external customers	0	0	0	0
Intersegment revenues	(2,510,872)	(2,234,064)	(5,070,184)	(4,432,294)
Investment income	47,133	40,027	93,703	83,380
Total revenues	(2,463,739)	(2,194,037)	(4,976,481)	(4,348,914)
Operating expenses, Benefits	(69,409)	(52,968)	(139,741)	(103,172)
Operating expenses, Operating costs	(2,420,438)	(2,167,490)	(4,896,150)	(4,291,671)
Operating expenses, Depreciation and amortization	(9,397)	(1,966)	(12,798)	(1,988)
Total operating expenses	(2,499,244)	(2,222,424)	(5,048,689)	(4,396,831)
Income from operations	35,505	28,387	72,208	47,917
Interest expense	27,663	26,222	54,891	52,536
Income before income taxes	7,842	2,165	17,317	(4,619)
Eliminations/Corporate [Member] | Medicare Advantage [Member]
Revenues - external customers, Premiums	0	0	0	0
Eliminations/Corporate [Member] | Medicare Stand-Alone PDP [Member]
Revenues - external customers, Premiums	0	0	0	0
Eliminations/Corporate [Member] | Medicare [Member]
Revenues - external customers, Premiums	0	0	0	0
Eliminations/Corporate [Member] | Fully-Insured [Member]
Revenues - external customers, Premiums	0	0	0	0
Eliminations/Corporate [Member] | Specialty [Member]
Revenues - external customers, Premiums	0	0	0	0
Eliminations/Corporate [Member] | Military Services [Member]
Revenues - external customers, Premiums	0	0	0	0
Eliminations/Corporate [Member] | Medicaid and Other [Member]
Revenues - external customers, Premiums	0	0	0	0
Eliminations/Corporate [Member] | Provider [Member]
Services revenue	0	0	0	0
Eliminations/Corporate [Member] | ASO and Other [Member]
Services revenue	0	0	0	0
Eliminations/Corporate [Member] | Pharmacy [Member]
Services revenue	0	0	0	0
Eliminations/Corporate [Member] | Services [Member]
Intersegment revenues	(2,077,003)	(1,927,081)	(4,201,675)	(3,838,398)
Medicare Advantage [Member]
Revenues - external customers, Premiums	5,319,758	4,885,209	10,641,138	9,702,189
Medicare Stand-Alone PDP [Member]
Revenues - external customers, Premiums	680,440	700,222	1,315,625	1,279,247
Medicare [Member]
Revenues - external customers, Premiums	6,000,198	5,585,431	11,956,763	10,981,436
Fully-Insured [Member]
Revenues - external customers, Premiums	1,422,892	1,484,020	2,822,370	2,990,838
Specialty [Member]
Revenues - external customers, Premiums	262,813	243,761	518,239	483,431
Military Services [Member]
Revenues - external customers, Premiums	934,738	885,368	1,858,015	1,730,362
Medicaid and Other [Member]
Revenues - external customers, Premiums	228,735	178,171	460,280	352,547
Provider [Member]
Services revenue	222,401	2,891	437,447	6,054
ASO and Other [Member]
Services revenue	118,496	129,811	236,185	259,668
Pharmacy [Member]
Services revenue	2,612	0	4,819	0
Services [Member]
Intersegment revenues	$ 0	$ 0	$ 0	$ 0