Schedule I Condensed Balance Sheets (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 11,981	$ 10,430	$ 10,923	$ 7,495
Total current assets	37,084	33,879
Other assets	3,575	3,037
Total assets	139,058	122,810	111,254
Current liabilities:
Accounts payable and accrued liabilities	15,180	13,361
Commercial paper and current maturities of long-term debt	2,857	7,193
Total current liabilities	50,463	49,252
Long-term debt, less current maturities	28,835	25,777
Long-term notes payable to subsidiaries	1,518	0
Other liabilities	5,556	4,831
Total liabilities	87,036	82,621
Commitments and contingencies (Note 4)
Shareholders’ equity:
Preferred stock, $0.001 par value - 10 shares authorized; no shares issued or outstanding	0	0
Common stock, $0.01 par value - 3,000 shares authorized; 969 and 952 issued and outstanding	10	10
Additional paid-in capital	1,703	0
Retained earnings	48,730	40,945
Accumulated other comprehensive loss	(2,667)	(2,681)
Total liabilities and shareholders’ equity	139,058	122,810
Parent Company [Member]
Current assets:
Cash and cash equivalents	359	180	$ 29	$ 559
Short-term notes receivable from subsidiaries	0	755
Other current assets	575	140
Total current assets	934	1,075
Equity in net assets of subsidiaries	76,231	60,593
Long-term notes receivable from subsidiaries	4,278	9,912
Other assets	839	248
Total assets	82,282	71,828
Current liabilities:
Accounts payable and accrued liabilities	502	452
Current portion of notes payable to subsidiaries	466	280
Commercial paper and current maturities of long-term debt	2,749	7,113
Total current liabilities	3,717	7,845
Long-term debt, less current maturities	28,318	25,657
Other liabilities	953	52
Total liabilities	34,506	33,554
Shareholders’ equity:
Preferred stock, $0.001 par value - 10 shares authorized; no shares issued or outstanding	0	0
Common stock, $0.01 par value - 3,000 shares authorized; 969 and 952 issued and outstanding	10	10
Additional paid-in capital	1,703	0
Retained earnings	48,730	40,945
Accumulated other comprehensive loss	(2,667)	(2,681)
Total UnitedHealth Group shareholders’ equity	47,776	38,274
Total liabilities and shareholders’ equity	$ 82,282	$ 71,828