Condensed Consolidated Statements of Changes in Shareholders' Equity (USD $) In Millions, unless otherwise specified	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Net Unrealized Investment Gain (Loss) [Member] Accumulated Other Comprehensive Income (Loss) [Member]	Foreign Currency Loss Accumulated Other Comprehensive Income (Loss) [Member]	Stockholders' Equity, Total [Member]
Balance at Dec. 31, 2011		$ 10	$ 0	$ 27,821	$ 476	$ (15)	$ 28,292
Balance (in shares) at Dec. 31, 2011		1,039
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings attributable to UnitedHealth Group common shareholders	4,282			4,282			4,282
Other Comprehensive (Loss) Income					108
Foreign currency translation losses	6					6
Other Comprehensive Income (Loss), Net of Tax	114						114
Issuances of common stock, and related tax benefits (in shares)		21
Issuances of common stock, and related tax benefits		0	273				273
Share-based compensation, and related tax benefits			459				459
Common stock repurchases (in shares)		(48)
Common stock repurchases		0	(732)	(1,862)			(2,594)
Cash dividends paid on common stock				(603)			(603)
Balance at Sep. 30, 2012		10	0	29,638	584	(9)	30,223
Balance (in shares) at Sep. 30, 2012		1,012
Balance at Dec. 31, 2012	31,178	10	66	30,664	516	(78)	31,178
Balance (in shares) at Dec. 31, 2012	1,019	1,019
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings attributable to UnitedHealth Group common shareholders	4,198			4,198			4,198
Other Comprehensive (Loss) Income					(390)
Foreign currency translation losses	(635)					(635)
Other Comprehensive Income (Loss), Net of Tax	(1,025)						(1,025)
Issuances of common stock, and related tax benefits (in shares)		16
Issuances of common stock, and related tax benefits		0	397				397
Share-based compensation, and related tax benefits			312				312
Acquisition of noncontrolling interest adn related tax effects			81				81
Common stock repurchases (in shares)	(37)	(37)
Common stock repurchases		0	(856)	(1,492)			(2,348)
Cash dividends paid on common stock				(777)			(777)
Balance at Sep. 30, 2013	$ 32,016	$ 10	$ 0	$ 32,593	$ 126	$ (713)	$ 32,016
Balance (in shares) at Sep. 30, 2013	998	998