Income Taxes Components of deferred income tax assets and liabilities (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Share-based compensation	$ 417	$ 385
Accrued expenses and allowances	259	233
Net operating loss carryforwards	247	285
Medical costs payable and other policy liabilities	166	102
Long term liabilities	155	147
Unearned revenues	56	78
Unrecognized tax benefits	44	62
Other	192	215
Subtotal	1,536	1,507
Less: valuation allowances	(184)	(247)
Total deferred income tax assets	1,352	1,260
Intangible assets	(1,148)	(1,104)
Capitalized software development	(465)	(450)
Net unrealized gains on investments	(275)	(161)
Depreciation and amortization	(256)	(140)
Prepaid expenses	(86)	(92)
Total deferred income tax liabilities	(2,230)	(1,947)
Net deferred income tax liabilities	$ (878)	$ (687)