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 Gain (Loss) [Member] 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	1,388			1,388			1,388
Other Comprehensive Income (Loss)	19				(6)
Foreign currency translation gains	3					3
Other Comprehensive Income (Loss), Net of Tax	(3)						(3)
Issuances of common stock, and related tax benefits (in shares)		13
Issuances of common stock, and related tax benefits		0	129				129
Common stock repurchases (in shares)		(19)
Common stock repurchases		0	(338)	(653)			(991)
Share-based compensation, and related tax benefits			209				209
Common stock dividends				(168)			(168)
Balance at Mar. 31, 2012		10	0	28,388	470	(12)	28,856
Balance (in shares) at Mar. 31, 2012		1,033
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	1,192			1,192			1,192
Other Comprehensive Income (Loss)	(32)				(68)
Foreign currency translation gains	18					18
Other Comprehensive Income (Loss), Net of Tax	(50)						(50)
Issuances of common stock, and related tax benefits (in shares)		4
Issuances of common stock, and related tax benefits		0	84				84
Common stock repurchases (in shares)		(10)
Common stock repurchases		0	(262)	(281)			(543)
Share-based compensation, and related tax benefits			112				112
Common stock dividends				(216)			(216)
Balance at Mar. 31, 2013	$ 31,757	$ 10	$ 0	$ 31,359	$ 448	$ (60)	$ 31,757
Balance (in shares) at Mar. 31, 2013	1,013	1,013