UnitedHealth (UNH) 10-K 12 Feb 19 2018 FY Annual report Financial data

Document and Entity Information

Document and Entity Information Document - USD ($)	12 Months Ended
	Dec. 31, 2018	Jan. 31, 2019	Jun. 30, 2018
Document Information [Line Items]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	FY
Entitiy Registrant Name	UNITEDHEALTH GROUP INC
Entitiy Central Index Key	731,766
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Well known seasoned issuer	Yes
Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		959,538,515
Closing Share Price			$ 245.34
Public Float			$ 234,490,429,732

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 10,866	$ 11,981
Short-term investments	3,458	3,509
Accounts receivable, net of allowances of $712 and $641	11,388	9,568
Other current receivables, net of allowances of $502 and $440	6,862	6,262
Assets under management	3,032	3,101
Prepaid expenses and other current assets	3,086	2,663
Total current assets	38,692	37,084
Long-term investments	32,510	28,341
Property, equipment and capitalized software, net of accumulated depreciation and amortization of $4,141 and $3,694	8,458	7,013
Goodwill	58,910	54,556
Other intangible assets, net of accumulated amortization of $4,592 and $4,309	9,325	8,489
Other assets	4,326	3,575
Total assets	152,221	139,058
Current liabilities:
Medical costs payable	19,891	17,871
Accounts payable and accrued liabilities	16,705	15,180
Commercial paper and current maturities of long-term debt	1,973	2,857
Unearned revenues	2,396	2,269
Other current liabilities	12,244	12,286
Total current liabilities	53,209	50,463
Long-term debt, less current maturities	34,581	28,835
Deferred income taxes	2,474	2,182
Other liabilities	5,730	5,556
Total liabilities	95,994	87,036
Commitments and contingencies (Note 12)
Redeemable noncontrolling interests	1,908	2,189
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; 960 and 969 issued and outstanding	10	10
Additional paid-in capital	0	1,703
Retained earnings	55,846	48,730
Accumulated other comprehensive loss	(4,160)	(2,667)
Nonredeemable noncontrolling interests	2,623	2,057
Total equity	54,319	49,833
Total liabilities, redeemable noncontrolling interests and equity	$ 152,221	$ 139,058

Consolidated Balance Sheet (Par

Consolidated Balance Sheet (Parenthetical) - USD ($) shares in Millions, $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Allowance for doubtful accounts, accounts receivable	$ 712	$ 641
Allowance for doubtful accounts, other receivables	502	440
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	4,141	3,694
Finite-lived Intangible Assets, Accumulated Amortization	$ 4,592	$ 4,309
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	3,000	3,000
Common stock, shares issued	960	969
Common Stock, shares outstanding	960	969
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	10	10
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues:
Premiums	$ 178,087	$ 158,453	$ 144,118
Products	29,601	26,366	26,658
Services	17,183	15,317	13,236
Investment and other income	1,376	1,023	828
Total revenues	226,247	201,159	184,840
Operating costs:
Medical costs	145,403	130,036	117,038
Operating costs	34,074	29,557	28,401
Cost of products sold	26,998	24,112	24,416
Depreciation and amortization	2,428	2,245	2,055
Total operating costs	208,903	185,950	171,910
Earnings from operations	17,344	15,209	12,930
Interest expense	(1,400)	(1,186)	(1,067)
Earnings before income taxes	15,944	14,023	11,863
Provision for income taxes	(3,562)	(3,200)	(4,790)
Net earnings	12,382	10,823	7,073
Earnings attributable to noncontrolling interests	(396)	(265)	(56)
Net earnings attributable to UnitedHealth Group common shareholders	$ 11,986	$ 10,558	$ 7,017
Earnings per share attributable to UnitedHealth Group common shareholders:
Basic	$ 12.45	$ 10.95	$ 7.37
Diluted	$ 12.19	$ 10.72	$ 7.25
Basic weighted-average number of common shares outstanding	963	964	952
Dilutive effect of common share equivalents	20	21	16
Diluted weighted-average number of common shares outstanding	983	985	968
Anti-dilutive shares excluded from the calculation of dilutive effect of common share equivalents	6	5	3

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net earnings	$ 12,382	$ 10,823	$ 7,073
Other comprehensive (loss) income:
Gross unrealized (losses) gains on investment securities during the period	(294)	209	(73)
Income tax effect	67	(72)	26
Total unrealized (losses) gains, net of tax	(227)	137	(47)
Gross reclassification adjustment for net realized gains included in net earnings	(62)	(83)	(166)
Income tax effect	14	30	60
Total reclassification adjustment, net of tax	(48)	(53)	(106)
Total foreign currency translation (losses) gains	(1,242)	(70)	806
Other comprehensive (loss) income	(1,517)	14	653
Comprehensive income	10,865	10,837	7,726
Comprehensive income attributable to noncontrolling interests	(396)	(265)	(56)
Comprehensive income attributable to UnitedHealth Group common shareholders	$ 10,469	$ 10,572	$ 7,670

Consolidated Statements of Chan

Consolidated Statements of Changes in Equity - USD ($) shares in Millions, $ in Millions	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Net Unrealized Gains (Losses) on Investments [Member]	Foreign Currency Translation (Losses) Gains [Member]	Nonredeemable noncontrolling interests [Member]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets	$ 28			$ 28
Balance at Dec. 31, 2015	33,725	$ 10	$ 29	37,125	$ 56	$ (3,390)	$ (105)
Balance (in shares) at Dec. 31, 2015		953
Net earnings attributable to UnitedHealth Group common shareholders	7,017			7,017
Net earnings attributable to nonredeemable noncontrolling interest							40
Net earnings, Including Portion Attributable to Nonredeemable Noncontrolling Interest	7,057
Other comprehensive (loss) income	653				(153)	806
Issuances of common stock, and related tax effects (in shares)		9
Issuances of common stock, and related tax effects	191	$ 0	191
Share-based compensation	455		455
Common share repurchases (in shares)		(10)
Common share repurchases	(1,280)	$ 0	(316)	(964)
Cash dividends paid on common shares ($3.45 per share, $2.875 per share and $2.375 per share for years ended December 31, 2018, December 31, 2017 and December 31, 2016, respectively)	(2,261)			(2,261)
Acquisition of redeemable noncontrolling interest shares	(143)		(143)
Redeemable noncontrolling interests fair value and other adjustments	(216)		(216)
Distributions to nonredeemable noncontrolling interests	(32)						(32)
Balance at Dec. 31, 2016	38,177	$ 10	0	40,945	(97)	(2,584)	(97)
Balance (in shares) at Dec. 31, 2016		952
Net earnings attributable to UnitedHealth Group common shareholders	10,558			10,558
Net earnings attributable to nonredeemable noncontrolling interest							194
Net earnings, Including Portion Attributable to Nonredeemable Noncontrolling Interest	10,752
Other comprehensive (loss) income	14				84	(70)
Issuances of common stock, and related tax effects (in shares)		26
Issuances of common stock, and related tax effects	2,225	$ 0	2,225
Share-based compensation	$ 582		582
Common share repurchases (in shares)	(9)	(9)
Common share repurchases	$ (1,500)	$ 0	(1,500)
Cash dividends paid on common shares ($3.45 per share, $2.875 per share and $2.375 per share for years ended December 31, 2018, December 31, 2017 and December 31, 2016, respectively)	(2,773)			(2,773)
Acquisition of redeemable noncontrolling interest shares	283		283
Redeemable noncontrolling interests fair value and other adjustments	113		113
Acquisition of nonredeemable noncontrolling interests	2,112						2,112
Distributions to nonredeemable noncontrolling interests	(152)						(152)
Balance at Dec. 31, 2017	$ 49,833	$ 10	1,703	48,730	(13)	(2,654)	2,057
Balance (in shares) at Dec. 31, 2017	969	969
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets	$ 0			(24)	24
Net earnings attributable to UnitedHealth Group common shareholders	11,986			11,986
Net earnings attributable to nonredeemable noncontrolling interest							273
Net earnings, Including Portion Attributable to Nonredeemable Noncontrolling Interest	12,259
Other comprehensive (loss) income	(1,517)				(275)	(1,242)
Issuances of common stock, and related tax effects (in shares)		10
Issuances of common stock, and related tax effects	814	$ 0	814
Share-based compensation	$ 620		620
Common share repurchases (in shares)	(19)	(19)
Common share repurchases	$ (4,500)	$ 0	(2,974)	(1,526)
Cash dividends paid on common shares ($3.45 per share, $2.875 per share and $2.375 per share for years ended December 31, 2018, December 31, 2017 and December 31, 2016, respectively)	(3,320)			(3,320)
Redeemable noncontrolling interests fair value and other adjustments	(163)		(163)
Acquisition of nonredeemable noncontrolling interests	521						521
Distributions to nonredeemable noncontrolling interests	(228)						(228)
Balance at Dec. 31, 2018	$ 54,319	$ 10	$ 0	$ 55,846	$ (264)	$ (3,896)	$ 2,623
Balance (in shares) at Dec. 31, 2018	960	960

Consolidated Statement of Chang

Consolidated Statement of Changes in Equity (Parentheticals) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Stockholders' Equity [Abstract]
Cash dividends per common share	$ 3.45	$ 2.875	$ 2.375

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating activities
Net earnings	$ 12,382	$ 10,823	$ 7,073
Noncash items:
Depreciation and amortization	2,428	2,245	2,055
Deferred income taxes	42	(965)	81
Share-based compensation	638	597	485
Other, net	(71)	217	(82)
Net change in other operating items, net of effects from acquisitions and changes in AARP balances:
Accounts receivable	(1,351)	(1,062)	(1,357)
Other assets	(750)	(630)	(1,601)
Medical costs payable	1,831	1,284	1,849
Accounts payable and other liabilities	526	930	1,494
Unearned revenues	38	157	(202)
Cash flows from operating activities	15,713	13,596	9,795
Investing activities
Purchases of investments	(14,010)	(14,588)	(17,547)
Sales of investments	3,641	4,623	7,339
Maturities of investments	6,270	5,646	4,281
Cash paid for acquisitions, net of cash assumed	(5,997)	(2,131)	(1,760)
Purchases of property, equipment and capitalized software	(2,063)	(2,023)	(1,705)
Other, net	(226)	(126)	37
Cash flows used for investing activities	(12,385)	(8,599)	(9,355)
Financing activities
Common share repurchases	(4,500)	(1,500)	(1,280)
Cash dividends paid	(3,320)	(2,773)	(2,261)
Proceeds from common stock issuances	838	688	429
Repayments of long-term debt	(2,600)	(4,398)	(2,596)
Repayments of commercial paper, net	(201)	(3,508)	(382)
Proceeds from issuance of long-term debt	6,935	5,291	3,968
Customer funds administered	(131)	3,172	1,692
Other, net	(1,386)	(413)	(581)
Cash flows used for financing activities	(4,365)	(3,441)	(1,011)
Effect of exchange rate changes on cash and cash equivalents	(78)	(5)	78
(Decrease) increase in cash and cash equivalents	(1,115)	1,551	(493)
Cash and cash equivalents, beginning of period	11,981	10,430	10,923
Cash and cash equivalents, end of period	10,866	11,981	10,430
Supplemental cash flow disclosures
Cash paid for interest	1,410	1,133	1,055
Cash paid for income taxes	3,257	4,004	4,726
Supplemental schedule of non-cash investing activities
Common stock issued for acquisitions	$ 0	$ 2,164	$ 0

Description of Business (Notes)

Description of Business (Notes)	12 Months Ended
	Dec. 31, 2018
Nature of Operations [Text Block]	Description of Business UnitedHealth Group Incorporated (individually and together with its subsidiaries, “UnitedHealth Group” and “the Company”) is a diversified health care company dedicated to helping people live healthier lives and helping make the health system work better for everyone. Through its diversified family of businesses, the Company leverages core competencies in data and health information; advanced technology; and clinical expertise. These core competencies are deployed within two distinct, but strategically aligned, business platforms: health benefits operating under UnitedHealthcare and health services operating under Optum.

Basis of Presentation, Uses of

Basis of Presentation, Uses of Estimates and Significant Accounting Policies (Notes)	12 Months Ended
	Dec. 31, 2018
Basis of Presentation and Significant Accounting Policies [Text Block]	Basis of Presentation, Use of Estimates and Significant Accounting Policies Basis of Presentation The Company has prepared the Consolidated Financial Statements according to U.S. Generally Accepted Accounting Principles (GAAP) and has included the accounts of UnitedHealth Group and its subsidiaries. Use of Estimates These Consolidated Financial Statements include certain amounts based on the Company’s best estimates and judgments. The Company’s most significant estimates relate to estimates and judgments for medical costs payable and revenues, valuation and impairment analysis of goodwill and other intangible assets and estimates of other current liabilities and other current receivables. Certain of these estimates require the application of complex assumptions and judgments, often because they involve matters that are inherently uncertain and will likely change in subsequent periods. The impact of any change in estimates is included in earnings in the period in which the estimate is adjusted. Revenues Premiums Premium revenues are primarily derived from risk-based health insurance arrangements in which the premium is typically at a fixed rate per individual served for a one-year period, and the Company assumes the economic risk of funding its customers’ health care and related administrative costs. Premium revenues are recognized in the period in which eligible individuals are entitled to receive health care benefits. Health care premium payments received from the Company’s customers in advance of the service period are recorded as unearned revenues. Fully insured commercial products of U.S. health plans, Medicare Advantage and Medicare Prescription Drug Benefit (Medicare Part D) plans with medical loss ratios as calculated under the definitions in the Patient Protection and Affordable Care Act (ACA) and related federal and state regulations and implementing regulation, that fall below certain targets are required to rebate ratable portions of their premiums annually. Medicare Advantage premium revenue includes the impact of the Centers for Medicare & Medicaid Services (CMS) quality bonuses based on plans’ Star ratings. Premium revenues are recognized based on the estimated premiums earned, net of projected rebates, because the Company is able to reasonably estimate the ultimate premiums of these contracts. The Company also records premium revenues from capitation arrangements at its OptumHealth businesses. The Company’s Medicare Advantage and Medicare Part D premium revenues are subject to periodic adjustment under CMS’ risk adjustment payment methodology. CMS deploys a risk adjustment model that apportions premiums paid to all health plans according to health severity and certain demographic factors. The CMS risk adjustment model provides higher per member payments for enrollees diagnosed with certain conditions and lower payments for enrollees who are healthier. Under this risk adjustment methodology, CMS calculates the risk adjusted premium payment using diagnosis data from hospital inpatient, hospital outpatient and physician treatment settings. The Company and health care providers collect, capture and submit the necessary and available diagnosis data to CMS within prescribed deadlines. The Company estimates risk adjustment premium revenues based upon the diagnosis data submitted and expected to be submitted to CMS. Risk adjustment data for the Company’s plans are subject to review by the government, including audit by regulators. See Note 12 for additional information regarding these audits. Products and Services For the Company’s OptumRx pharmacy care services business, the majority of revenues are derived from products sold through a contracted network of retail pharmacies or home delivery, specialty and compounding pharmacy facilities. Product revenues include ingredient costs (net of rebates), a negotiated dispensing fee and customer co-payments for drugs dispensed through the Company’s mail-service pharmacy. In retail pharmacy transactions, revenues recognized exclude the member’s applicable co-payment. Pharmacy products are billed to customers based on the number of transactions occurring during the billing period. Product revenues are recognized when the prescriptions are dispensed through the retail network or received by consumers through the Company’s mail-service pharmacy. The Company has entered into contracts in which it is primarily obligated to pay its network pharmacy providers for benefits provided to their customers regardless of whether the Company is paid. The Company is also involved in establishing the prices charged by retail pharmacies, determining which drugs will be included in formulary listings and selecting which retail pharmacies will be included in the network offered to plan sponsors’ members and accordingly, are reported on a gross basis. Services revenue consists of fees derived from services performed for customers that self-insure the health care costs of their employees and employees’ dependents. Under service fee contracts, the Company receives monthly, a fixed fee per employee, which is recognized as revenue as the Company performs, or makes available, the applicable services to the customer. The customers retain the risk of financing health care costs for their employees and employees’ dependents, and the Company administers the payment of customer funds to physicians and other health care professionals from customer-funded bank accounts. As the Company has neither the obligation for funding the health care costs, nor the primary responsibility for providing the medical care, the Company does not recognize premium revenue and medical costs for these contracts in its Consolidated Financial Statements. For these fee-based customer arrangements, the Company provides coordination and facilitation of medical services; transaction processing; customer, consumer and care professional services; and access to contracted networks of physicians, hospitals and other health care professionals. These services are performed throughout the contract period. Revenues are also comprised of a number of services and products sold through Optum. OptumHealth’s service revenues include net patient service revenues that are recorded based upon established billing rates, less allowances for contractual adjustments, and are recognized as services are provided. For its financial services offerings, OptumHealth charges fees and earns investment income on managed funds. OptumInsight provides software and information products, advisory consulting arrangements and services outsourcing contracts, which may be delivered over several years. OptumInsight revenues are generally recognized over time and measured each period based on the progress to date as services are performed or made available to customers. As of December 31, 2018 and 2017 , accounts receivables related to products and services were $3.9 billion and $3.7 billion , respectively. In 2018 and 2017 , the Company had no material bad-debt expense and there were no material contract assets, contract liabilities or deferred contract costs recorded on the Consolidated Balance Sheets as of December 31, 2018 or 2017 . For the years ended December 31, 2018 and 2017 , revenue recognized from performance obligations related to prior periods (for example, due to changes in transaction price) was not material. Revenue expected to be recognized in any future year related to remaining performance obligations, excluding revenue pertaining to contracts that have an original expected duration of one year or less, contracts where revenue is recognized as invoiced and contracts with variable consideration related to undelivered performance obligations, is not material. See Note 13 for disaggregation of revenue by segment and type. Medical Costs and Medical Costs Payable The Company’s estimate of medical costs payable represents management’s best estimate of its liability for unpaid medical costs as of December 31, 2018. Each period, the Company re-examines previously established medical costs payable estimates based on actual claim submissions and other changes in facts and circumstances. As more complete claim information becomes available, the Company adjusts the amount of the estimates and includes the changes in estimates in medical costs in the period in which the change is identified. Approximately 90% of claims related to medical care services are known and settled within 90 days from the date of service and substantially all within twelve months. Medical costs and medical costs payable include estimates of the Company’s obligations for medical care services that have been rendered on behalf of insured consumers, but for which claims have either not yet been received, processed, or paid. The Company develops estimates for medical care services incurred but not reported (IBNR), which includes estimates for claims that have not been received or fully processed, using an actuarial process that is consistently applied, centrally controlled and automated. The actuarial models consider factors such as time from date of service to claim processing, seasonal variances in medical care consumption, health care professional contract rate changes, medical care utilization and other medical cost trends, membership volume and demographics, the introduction of new technologies, benefit plan changes, and business mix changes related to products, customers and geography. In developing its medical costs payable estimates, the Company applies different estimation methods depending on which incurred claims are being estimated. For the most recent two months, the Company estimates claim costs incurred by applying observed medical cost trend factors to the average per member per month (PMPM) medical costs incurred in prior months for which more complete claim data are available, supplemented by a review of near-term completion factors (actuarial estimates, based upon historical experience and analysis of current trends, of the percentage of incurred claims during a given period that have been adjudicated by the Company at the date of estimation). For months prior to the most recent two months, the Company applies the completion factors to actual claims adjudicated-to-date to estimate the expected amount of ultimate incurred claims for those months. Cost of Products Sold The Company’s cost of products sold includes the cost of pharmaceuticals dispensed to unaffiliated customers either directly at its home delivery and specialty pharmacy locations, or indirectly through its nationwide network of participating pharmacies. Rebates attributable to non-affiliated clients are accrued as rebates receivable and a reduction of cost of products sold, with a corresponding payable for the amounts of the rebates to be remitted to those non-affiliated clients in accordance with their contracts and recorded in the Consolidated Statements of Operations as a reduction of product revenue. Cost of products sold also includes the cost of personnel to support the Company’s transaction processing services, system sales, maintenance and professional services. Cash, Cash Equivalents and Investments Cash and cash equivalents are highly liquid investments that have an original maturity of three months or less. The fair value of cash and cash equivalents approximates their carrying value because of the short maturity of the instruments. Investments with maturities of less than one year are classified as short-term. Because of regulatory requirements, certain investments are included in long-term investments regardless of their maturity date. The Company classifies these investments as held-to-maturity and reports them at amortized cost. Substantially all other investments are classified as available-for-sale and reported at fair value based on quoted market prices, where available. Equity investments, with certain exceptions, are measured at fair value with changes in fair value recognized in net earnings. The Company excludes unrealized gains and losses on investments in available-for-sale debt securities from net earnings and reports them as comprehensive income and, net of income tax effects, as a separate component of equity. To calculate realized gains and losses on the sale of debt securities, the Company specifically identifies the cost of each investment sold. The Company evaluates an investment for impairment by considering the length of time and extent to which market value has been less than cost or amortized cost, the financial condition and near-term prospects of the issuer as well as specific events or circumstances that may influence the operations of the issuer and the Company’s intent to sell the security or the likelihood that it will be required to sell the security before recovery of the entire amortized cost. New information and the passage of time can change these judgments. The Company manages its investment portfolio to limit its exposure to any one issuer or market sector, and largely limits its investments to investment grade quality. Securities downgraded below policy minimums after purchase will be disposed of in accordance with the Company’s investment policy. Assets Under Management The Company provides health insurance products and services to members of AARP under a Supplemental Health Insurance Program (the AARP Program) and to AARP members and non-members under separate Medicare Advantage and Medicare Part D arrangements. The products and services under the AARP Program include supplemental Medicare benefits, hospital indemnity insurance, including insurance for individuals between 50 to 64 years of age, and other related products. Pursuant to the Company’s agreement, AARP Program assets are managed separately from the Company’s general investment portfolio and are used to pay costs associated with the AARP Program. These assets are invested at the Company’s discretion, within investment guidelines approved by AARP. The Company does not guarantee any rates of return on these investments and, upon any transfer of the AARP Program contract to another entity, the Company would transfer cash equal in amount to the fair value of these investments at the date of transfer to that entity. Because the purpose of these assets is to fund the medical costs payable, the rate stabilization fund (RSF) liabilities and other related liabilities associated with this AARP contract, assets under management are classified as current assets, consistent with the classification of these liabilities. The effects of changes in other balance sheet amounts associated with the AARP Program also accrue to the overall benefit of the AARP policyholders through the RSF balance. Accordingly, the Company excludes the effect of such changes in its Consolidated Statements of Cash Flows. Other Current Receivables Other current receivables include amounts due from pharmaceutical manufacturers for rebates and other miscellaneous amounts due to the Company. The Company’s pharmacy care services businesses contract with pharmaceutical manufacturers, some of which provide rebates based on use of the manufacturers’ products by its affiliated and non-affiliated clients. The Company accrues rebates as they are earned by its clients on a monthly basis based on the terms of the applicable contracts, historical data and current estimates. The pharmacy care services businesses bill these rebates to the manufacturers on a monthly or quarterly basis depending on the contractual terms and record rebates attributable to affiliated clients as a reduction to medical costs. The Company generally receives rebates two to five months after billing. As of December 31, 2018 and 2017, total pharmaceutical manufacturer rebates receivable included in other receivables in the Consolidated Balance Sheets amounted to $4.2 billion and $3.8 billion , respectively. Property, Equipment and Capitalized Software Property, equipment and capitalized software are stated at cost, net of accumulated depreciation and amortization. Capitalized software consists of certain costs incurred in the development of internal-use software, including external direct costs of materials and services and applicable payroll costs of employees devoted to specific software development. The Company calculates depreciation and amortization using the straight-line method over the estimated useful lives of the assets. The useful lives for property, equipment and capitalized software are: Furniture, fixtures and equipment 3 to 10 years Buildings 35 to 40 years Capitalized software 3 to 5 years Leasehold improvements are depreciated over the shorter of the remaining lease term or their estimated useful economic life. Goodwill To determine whether goodwill is impaired, annually or more frequently if needed, the Company performs a multi-step impairment test. The Company may first assess qualitative factors to determine if it is more likely than not that the carrying value of a reporting unit exceeds its estimated fair value. The Company may also elect to skip the qualitative testing and proceed directly to the quantitative testing. When performing quantitative testing, the Company first estimates the fair values of its reporting units using discounted cash flows. To determine fair values, the Company must make assumptions about a wide variety of internal and external factors. Significant assumptions used in the impairment analysis include financial projections of free cash flow (including significant assumptions about operations, capital requirements and income taxes), long-term growth rates for determining terminal value and discount rates. Comparative market multiples are used to corroborate the results of the discounted cash flow test. If the fair value is less than the carrying value of the reporting unit, then the implied value of goodwill would be calculated and compared to the carrying amount of goodwill to determine whether goodwill is impaired. There was no impairment of goodwill during the year ended December 31, 2018 . Intangible Assets The Company’s intangible assets are subject to impairment tests when events or circumstances indicate that an intangible asset (or asset group) may be impaired. The Company’s indefinite-lived intangible assets are also tested for impairment annually. There was no impairment of intangible assets during the year ended December 31, 2018 . Other Current Liabilities Other current liabilities include health savings account deposits ( $7.5 billion and $6.4 billion as of December 31, 2018 and 2017 , respectively), deposits under the Medicare Part D program, the RSF associated with the AARP Program, accruals for premium rebate payments under the ACA, the current portion of future policy benefits and customer balances. Policy Acquisition Costs The Company’s short duration health insurance contracts typically have a one-year term and may be canceled by the customer with at least 30 days’ notice. Costs related to the acquisition and renewal of short duration customer contracts are primarily charged to expense as incurred. Redeemable Noncontrolling Interests Redeemable noncontrolling interests in the Company’s subsidiaries whose redemption is outside the control of the Company are classified as temporary equity. The following table provides details of the Company's redeemable noncontrolling interests’ activity for the years ended December 31, 2018 and 2017 : (in millions) 2018 2017 Redeemable noncontrolling interests, beginning of period $ 2,189 $ 2,012 Net earnings 123 71 Acquisitions 102 565 Redemptions (90 ) (309 ) Distributions (53 ) (38 ) Fair value and other adjustments (363 ) (112 ) Redeemable noncontrolling interests, end of period $ 1,908 $ 2,189 Share-Based Compensation The Company recognizes compensation expense for share-based awards, including stock options, stock-settled stock appreciation rights (SARs) and restricted stock and restricted stock units (collectively, restricted shares), on a straight-line basis over the related service period (generally the vesting period) of the award, or to an employee’s eligible retirement date under the award agreement, if earlier. Restricted shares vest ratably, primarily over two to five years and compensation expense related to restricted shares is based on the share price on the date of grant. Stock options and SARs vest ratably primarily over four years and may be exercised up to 10 years from the date of grant. Compensation expense related to stock options and SARs is based on the fair value at the date of grant, which is estimated on the date of grant using a binomial option-pricing model. Under the Company’s Employee Stock Purchase Plan (ESPP), eligible employees are allowed to purchase the Company’s stock at a discounted price, which is 85% of the lower market price of the Company’s common stock at the beginning or at the end of the six-month purchase period. Share-based compensation expense for all programs is recognized in operating costs in the Consolidated Statements of Operations. Net Earnings Per Common Share The Company computes basic earnings per common share attributable to UnitedHealth Group common shareholders by dividing net earnings attributable to UnitedHealth Group common shareholders by the weighted-average number of common shares outstanding during the period. The Company determines diluted net earnings per common share attributable to UnitedHealth Group common shareholders using the weighted-average number of common shares outstanding during the period, adjusted for potentially dilutive shares associated with stock options, SARs, restricted shares and the ESPP (collectively, common stock equivalents), using the treasury stock method. The treasury stock method assumes a hypothetical issuance of shares to settle the share-based awards, with the assumed proceeds used to purchase common stock at the average market price for the period. Assumed proceeds include the amount the employee must pay upon exercise and the average unrecognized compensation cost. The difference between the number of shares assumed issued and number of shares assumed purchased represents the dilutive shares. Health Insurance Industry Tax The ACA includes an annual, nondeductible insurance industry tax (Health Insurance Industry Tax) to be levied proportionally across the insurance industry for risk-based health insurance products. A one year moratorium on the collection of the Health Insurance Industry Tax will occur in 2019. The Company estimates its liability for the Health Insurance Industry Tax based on a ratio of the Company’s applicable net premiums written compared to the U.S. health insurance industry total applicable net premiums, both for the previous calendar year. The Company records in full the estimated liability for the Health Insurance Industry Tax at the beginning of the calendar year with a corresponding deferred cost that is amortized to operating costs on the Consolidated Statements of Operations using a straight-line method over the calendar year. The liability is recorded in accounts payable and accrued liabilities and the corresponding deferred cost is recorded in prepaid expenses and other current assets on the Consolidated Balance Sheets. Recently Issued Accounting Standards In February 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standard Update (ASU) No. 2016-02, “Leases (Topic 842)” as modified by ASUs 2018-01, 2018-10, 2018-11 and 2018-20 (collectively, ASU 2016-02). Under ASU 2016-02, an entity is required to recognize assets and liabilities for the rights and obligations created by leases on the entity’s balance sheet for both finance and operating leases. For leases with a term of 12 months or less, the Company elected to not recognize lease assets and lease liabilities and expense the leases over a straight-line basis for the term of those leases. ASU 2016-02 requires new disclosures that depict the amount, timing and uncertainty of cash flows pertaining to an entity’s leases. The Company adopted ASU 2016-02 on January 1, 2019, using the cumulative effect upon adoption approach. The adoption resulted in no material impact to the Company’s balance sheet, results of operations, equity or cash flows. Recently Adopted Accounting Standards In January 2016, the FASB issued ASU 2016-01, “Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities” (ASU 2016-01). Most notably, the new guidance requires that equity investments, with certain exemptions, be measured at fair value with changes in fair value recognized in net income as opposed to other comprehensive income. The Company adopted ASU 2016-01 on a prospective basis effective January 1, 2018, as required, and reclassified $ 24 million from accumulated other comprehensive income to retained earnings. The Company has determined that there have been no other recently adopted or issued accounting standards that had, or will have, a material impact on its Consolidated Financial Statements.

Investments (Notes)

Investments (Notes)	12 Months Ended
	Dec. 31, 2018
Investments [Abstract]
Investments [Text Block]	Investments A summary of debt securities by major security type is as follows: (in millions) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value December 31, 2018 Debt securities - available-for-sale: U.S. government and agency obligations $ 3,434 $ 13 $ (42 ) $ 3,405 State and municipal obligations 7,117 61 (57 ) 7,121 Corporate obligations 15,366 14 (218 ) 15,162 U.S. agency mortgage-backed securities 4,947 11 (106 ) 4,852 Non-U.S. agency mortgage-backed securities 1,376 2 (20 ) 1,358 Total debt securities - available-for-sale 32,240 101 (443 ) 31,898 Debt securities - held-to-maturity: U.S. government and agency obligations 255 1 (2 ) 254 State and municipal obligations 11 — — 11 Corporate obligations 355 — — 355 Total debt securities - held-to-maturity 621 1 (2 ) 620 Total debt securities $ 32,861 $ 102 $ (445 ) $ 32,518 December 31, 2017 Debt securities - available-for-sale: U.S. government and agency obligations $ 2,673 $ 1 $ (30 ) $ 2,644 State and municipal obligations 7,596 99 (35 ) 7,660 Corporate obligations 13,181 57 (44 ) 13,194 U.S. agency mortgage-backed securities 3,942 7 (38 ) 3,911 Non-U.S. agency mortgage-backed securities 1,018 3 (6 ) 1,015 Total debt securities - available-for-sale 28,410 167 (153 ) 28,424 Debt securities - held-to-maturity: U.S. government and agency obligations 254 1 (1 ) 254 State and municipal obligations 2 — — 2 Corporate obligations 280 — — 280 Total debt securities - held-to-maturity 536 1 (1 ) 536 Total debt securities $ 28,946 $ 168 $ (154 ) $ 28,960 Nearly all of the Company’s investments in mortgage-backed securities were rated AAA as of December 31, 2018 . The Company held $2.0 billion of equity securities as of December 31, 2018 and December 31, 2017. The Company’s investments in equity securities primarily consist of employee savings plan related investments, Brazilian real denominated fixed-income funds and dividend paying stocks, with readily determinable fair values. Additionally, the Company’s investments included $ 1.5 billion and $ 0.9 billion of equity method investments in operating businesses in the health care sector, as of December 31, 2018 and 2017, respectively. The amortized cost and fair value of debt securities as of December 31, 2018 , by contractual maturity, were as follows: Available-for-Sale Held-to-Maturity (in millions) Amortized Cost Fair Value Amortized Fair Due in one year or less $ 3,560 $ 3,551 $ 150 $ 150 Due after one year through five years 12,432 12,297 213 212 Due after five years through ten years 7,362 7,270 129 129 Due after ten years 2,563 2,570 129 129 U.S. agency mortgage-backed securities 4,947 4,852 — — Non-U.S. agency mortgage-backed securities 1,376 1,358 — — Total debt securities $ 32,240 $ 31,898 $ 621 $ 620 The fair value of available-for-sale investments with gross unrealized losses by major security type and length of time that individual securities have been in a continuous unrealized loss position were as follows: Less Than 12 Months 12 Months or Greater Total (in millions) Fair Value Gross Unrealized Losses Fair Value Gross Fair Value Gross December 31, 2018 Debt securities - available-for-sale: U.S. government and agency obligations $ 998 $ (7 ) $ 1,425 $ (35 ) $ 2,423 $ (42 ) State and municipal obligations 1,334 (11 ) 2,491 (46 ) 3,825 (57 ) Corporate obligations 8,105 (109 ) 4,239 (109 ) 12,344 (218 ) U.S. agency mortgage-backed securities 1,296 (22 ) 2,388 (84 ) 3,684 (106 ) Non-U.S. agency mortgage-backed securities 622 (7 ) 459 (13 ) 1,081 (20 ) Total debt securities - available-for-sale $ 12,355 $ (156 ) $ 11,002 $ (287 ) $ 23,357 $ (443 ) December 31, 2017 Debt securities - available-for-sale: U.S. government and agency obligations $ 1,249 $ (8 ) $ 1,027 $ (22 ) $ 2,276 $ (30 ) State and municipal obligations 2,599 (21 ) 866 (14 ) 3,465 (35 ) Corporate obligations 5,901 (23 ) 1,242 (21 ) 7,143 (44 ) U.S. agency mortgage-backed securities 1,657 (12 ) 1,162 (26 ) 2,819 (38 ) Non-U.S. agency mortgage-backed securities 411 (3 ) 144 (3 ) 555 (6 ) Total debt securities - available-for-sale $ 11,817 $ (67 ) $ 4,441 $ (86 ) $ 16,258 $ (153 ) The Company’s unrealized losses from all securities as of December 31, 2018 were generated from approximately 19,000 positions out of a total of 31,000 positions. The Company believes that it will collect the principal and interest due on its debt securities that have an amortized cost in excess of fair value. The unrealized losses were primarily caused by interest rate increases and not by unfavorable changes in the credit quality associated with these securities. At each reporting period, the Company evaluates securities for impairment when the fair value of the investment is less than its amortized cost. The Company evaluated the underlying credit quality and credit ratings of the issuers, noting no significant deterioration since purchase. As of December 31, 2018 , the Company did not have the intent to sell any of the securities in an unrealized loss position. Therefore, the Company believes these losses to be temporary.

Fair Value (Notes)

Fair Value (Notes)	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value [Text Block]	Fair Value Certain assets and liabilities are measured at fair value in the Consolidated Financial Statements or have fair values disclosed in the Notes to the Consolidated Financial Statements. These assets and liabilities are classified into one of three levels of a hierarchy defined by GAAP. In instances in which the inputs used to measure fair value fall into different levels of the fair value hierarchy, the fair value measurement is categorized in its entirety based on the lowest level input that is significant to the fair value measurement in its entirety. The Company’s assessment of the significance of a particular item to the fair value measurement in its entirety requires judgment, including the consideration of inputs specific to the asset or liability. The fair value hierarchy is summarized as follows: Level 1 — Quoted prices (unadjusted) for identical assets/liabilities in active markets. Level 2 — Other observable inputs, either directly or indirectly, including: • Quoted prices for similar assets/liabilities in active markets; • Quoted prices for identical or similar assets/liabilities in inactive markets (e.g., few transactions, limited information, noncurrent prices, high variability over time); • Inputs other than quoted prices that are observable for the asset/liability (e.g., interest rates, yield curves, implied volatilities, credit spreads); and • Inputs that are corroborated by other observable market data. Level 3 — Unobservable inputs that cannot be corroborated by observable market data. There was no transfers in or out of Level 3 financial assets or liabilities during the year ended December 31, 2018 or 2017 . Nonfinancial assets and liabilities or financial assets and liabilities that are measured at fair value on a nonrecurring basis are subject to fair value adjustments only in certain circumstances, such as when the Company records an impairment. There were no significant fair value adjustments for these assets and liabilities recorded during the year ended December 31, 2018 or 2017 . The following methods and assumptions were used to estimate the fair value and determine the fair value hierarchy classification of each class of financial instrument included in the tables below: Cash and Cash Equivalents. The carrying value of cash and cash equivalents approximates fair value as maturities are less than three months. Fair values of cash equivalent instruments that do not trade on a regular basis in active markets are classified as Level 2. Debt and Equity Securities. Fair values of debt and equity securities are based on quoted market prices, where available. The Company obtains one price for each security primarily from a third-party pricing service (pricing service), which generally uses quoted or other observable inputs for the determination of fair value. The pricing service normally derives the security prices through recently reported trades for identical or similar securities, and, if necessary, makes adjustments through the reporting date based upon available observable market information. For securities not actively traded, the pricing service may use quoted market prices of comparable instruments or discounted cash flow analyses, incorporating inputs that are currently observable in the markets for similar securities. Inputs that are often used in the valuation methodologies include, but are not limited to, benchmark yields, credit spreads, default rates, prepayment speeds and nonbinding broker quotes. As the Company is responsible for the determination of fair value, it performs quarterly analyses on the prices received from the pricing service to determine whether the prices are reasonable estimates of fair value. Specifically, the Company compares the prices received from the pricing service to prices reported by a secondary pricing source, such as its custodian, its investment consultant and third-party investment advisors. Additionally, the Company compares changes in the reported market values and returns to relevant market indices to test the reasonableness of the reported prices. The Company’s internal price verification procedures and reviews of fair value methodology documentation provided by independent pricing services have not historically resulted in adjustment in the prices obtained from the pricing service. Fair values of debt securities that do not trade on a regular basis in active markets but are priced using other observable inputs are classified as Level 2. Fair value estimates for Level 1 and Level 2 equity securities are based on quoted market prices for actively traded equity securities and/or other market data for the same or comparable instruments and transactions in establishing the prices. The fair values of Level 3 investments in corporate bonds are estimated using valuation techniques that rely heavily on management assumptions and qualitative observations. Throughout the procedures discussed above in relation to the Company’s processes for validating third-party pricing information, the Company validates the understanding of assumptions and inputs used in security pricing and determines the proper classification in the hierarchy based on that understanding. Assets Under Management. Assets under management consists of debt securities and other investments held to fund costs associated with the AARP Program and are priced and classified using the same methodologies as the Company’s investments in debt and equity securities. Long-Term Debt. The fair values of the Company’s long-term debt are estimated and classified using the same methodologies as the Company’s investments in debt securities. The following table presents a summary of fair value measurements by level and carrying values for items measured at fair value on a recurring basis in the Consolidated Balance Sheets: (in millions) Quoted Prices in Active Markets (Level 1) Other Observable Inputs (Level 2) Unobservable Inputs (Level 3) Total Fair and Carrying Value December 31, 2018 Cash and cash equivalents $ 10,757 $ 109 $ — $ 10,866 Debt securities - available-for-sale: U.S. government and agency obligations 3,060 345 — 3,405 State and municipal obligations — 7,121 — 7,121 Corporate obligations 39 14,950 173 15,162 U.S. agency mortgage-backed securities — 4,852 — 4,852 Non-U.S. agency mortgage-backed securities — 1,358 — 1,358 Total debt securities - available-for-sale 3,099 28,626 173 31,898 Equity securities 1,832 13 — 1,845 Assets under management 1,086 1,938 8 3,032 Total assets at fair value $ 16,774 $ 30,686 $ 181 $ 47,641 Percentage of total assets at fair value 35 % 65 % — % 100 % December 31, 2017 Cash and cash equivalents $ 11,718 $ 263 $ — $ 11,981 Debt securities - available-for-sale: U.S. government and agency obligations 2,428 216 — 2,644 State and municipal obligations — 7,660 — 7,660 Corporate obligations 65 12,989 140 13,194 U.S. agency mortgage-backed securities — 3,911 — 3,911 Non-U.S. agency mortgage-backed securities — 1,015 — 1,015 Total debt securities - available-for-sale 2,493 25,791 140 28,424 Equity securities 1,784 14 194 1,992 Assets under management 1,117 1,984 — 3,101 Total assets at fair value $ 17,112 $ 28,052 $ 334 $ 45,498 Percentage of total assets at fair value 38 % 61 % 1 % 100 % The following table presents a summary of fair value measurements by level and carrying values for certain financial instruments not measured at fair value on a recurring basis in the Consolidated Balance Sheets: (in millions) Quoted Prices in Active Markets (Level 1) Other Observable Inputs (Level 2) Unobservable Inputs (Level 3) Total Fair Value Total Carrying Value December 31, 2018 Debt securities - held-to-maturity $ 260 $ 65 $ 295 $ 620 $ 621 Long-term debt and other financing obligations $ — $ 37,944 $ — $ 37,944 $ 36,554 December 31, 2017 Debt securities - held-to-maturity $ 267 $ 4 $ 265 $ 536 $ 536 Long-term debt and other financing obligations $ — $ 34,504 $ — $ 34,504 $ 31,542 The carrying amounts reported on the Consolidated Balance Sheets for other current financial assets and liabilities approximate fair value because of their short-term nature. These assets and liabilities are not listed in the table above.

Property, Plant, and Capitalize

Property, Plant, and Capitalized Software (Notes)	12 Months Ended
	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment Disclosure [Text Block]	Property, Equipment and Capitalized Software A summary of property, equipment and capitalized software is as follows: (in millions) December 31, 2018 December 31, 2017 Land and improvements $ 566 $ 405 Buildings and improvements 4,470 3,664 Computer equipment 1,984 1,829 Furniture and fixtures 1,525 1,208 Less accumulated depreciation (2,787 ) (2,488 ) Property and equipment, net 5,758 4,618 Capitalized software 4,054 3,601 Less accumulated amortization (1,354 ) (1,206 ) Capitalized software, net 2,700 2,395 Total property, equipment and capitalized software, net $ 8,458 $ 7,013 Depreciation expense for property and equipment for the years ended December 31, 2018 , 2017 and 2016 was $924 million , $799 million and $698 million , respectively. Amortization expense for capitalized software for the years ended December 31, 2018 , 2017 and 2016 was $606 million , $550 million and $475 million , respectively.

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Notes)	12 Months Ended
	Dec. 31, 2018
Goodwill [Line Items]
Goodwill Disclosure [Text Block]	Goodwill and Other Intangible Assets Changes in the carrying amount of goodwill, by reportable segment, were as follows: (in millions) UnitedHealthcare OptumHealth OptumInsight OptumRx Consolidated Balance at January 1, 2017 $ 23,854 $ 6,322 $ 4,449 $ 12,959 $ 47,584 Acquisitions 690 5,189 1,221 — 7,100 Foreign currency effects and adjustments, net (60 ) (23 ) 4 (49 ) (128 ) Balance at December 31, 2017 24,484 11,488 5,674 12,910 54,556 Acquisitions 2,723 471 106 1,881 5,181 Foreign currency effects and adjustments, net (807 ) (12 ) (8 ) — (827 ) Balance at December 31, 2018 $ 26,400 $ 11,947 $ 5,772 $ 14,791 $ 58,910 The gross carrying value, accumulated amortization and net carrying value of other intangible assets were as follows: December 31, 2018 December 31, 2017 (in millions) Gross Carrying Value Accumulated Amortization Net Carrying Value Gross Carrying Value Accumulated Amortization Net Carrying Value Customer-related $ 11,622 $ (3,908 ) $ 7,714 $ 10,832 $ (3,743 ) $ 7,089 Trademarks and technology 1,122 (512 ) 610 1,054 (432 ) 622 Trademarks and other indefinite-lived 745 — 745 561 — 561 Other 428 (172 ) 256 351 (134 ) 217 Total $ 13,917 $ (4,592 ) $ 9,325 $ 12,798 $ (4,309 ) $ 8,489 The acquisition date fair values and weighted-average useful lives assigned to finite-lived intangible assets acquired in business combinations consisted of the following by year of acquisition: 2018 2017 (in millions, except years) Fair Value Weighted-Average Useful Life Fair Value Weighted-Average Useful Life Customer-related $ 1,355 17 years $ 324 13 years Trademarks and technology 122 4 years 367 11 years Other 97 9 years 82 6 years Total acquired finite-lived intangible assets $ 1,574 16 years $ 773 11 years Estimated full year amortization expense relating to intangible assets for each of the next five years ending December 31 is as follows: (in millions) 2019 $ 889 2020 795 2021 724 2022 632 2023 593 Amortization expense relating to intangible assets for the years ended December 31, 2018 , 2017 and 2016 was $898 million , $896 million and $882 million , respectively.

Medical Costs Payable (Notes)

Medical Costs Payable (Notes)	12 Months Ended
	Dec. 31, 2018
Medical Costs Payable	Medical Costs Payable The following table shows the components of the change in medical costs payable for the years ended December 31: (in millions) 2018 2017 2016 Medical costs payable, beginning of period $ 17,871 $ 16,391 $ 14,330 Acquisitions 339 83 — Reported medical costs: Current year 145,723 130,726 117,258 Prior years (320 ) (690 ) (220 ) Total reported medical costs 145,403 130,036 117,038 Medical payments: Payments for current year (127,155 ) (113,811 ) (101,696 ) Payments for prior years (16,567 ) (14,828 ) (13,281 ) Total medical payments (143,722 ) (128,639 ) (114,977 ) Medical costs payable, end of period $ 19,891 $ 17,871 $ 16,391 For the years ended December 31, 2018 and 2016 , no individual factors significantly impacted medical cost reserve development . For the year ended December 31, 2017 , medical cost reserve development was primarily driven by lower than expected health system utilization levels. Medical costs payable included IBNR of $13.2 billion and $12.3 billion at December 31, 2018 and 2017 , respectively. Substantially all of the IBNR balance as of December 31, 2018 relates to the current year. The following is information about incurred and paid medical cost development as of December 31, 2018 : Net Incurred Medical Costs (in millions) For the Years ended December 31, Year 2017 2018 2017 $ 130,726 $ 130,441 2018 145,723 Total $ 276,164 Net Cumulative Medical Payments (in millions) For the Years ended December 31, Year 2017 2018 2017 $ (113,811 ) $ (129,778 ) 2018 (127,155 ) Total (256,933 ) Net remaining outstanding liabilities prior to 2017 660 Total medical costs payable $ 19,891

Commercial Paper and Long-Term

Commercial Paper and Long-Term Debt (Notes)	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Commercial Paper and Long-Term Debt [Text Block]	Commercial Paper and Long-Term Debt Commercial paper and senior unsecured long-term debt consisted of the following: December 31, 2018 December 31, 2017 (in millions, except percentages) Par Value Carrying Value Fair Value Par Value Carrying Value Fair Value Commercial paper $ — $ — $ — $ 150 $ 150 $ 150 6.000% notes due February 2018 — — — 1,100 1,101 1,106 1.900% notes due July 2018 — — — 1,500 1,499 1,501 1.700% notes due February 2019 750 750 749 750 749 747 1.625% notes due March 2019 500 500 499 500 501 497 2.300% notes due December 2019 500 494 497 500 495 501 2.700% notes due July 2020 1,500 1,498 1,494 1,500 1,496 1,517 Floating rate notes due October 2020 300 299 298 300 299 300 3.875% notes due October 2020 450 443 456 450 446 467 1.950% notes due October 2020 900 897 884 900 895 892 4.700% notes due February 2021 400 398 412 400 403 425 2.125% notes due March 2021 750 747 734 750 746 744 Floating rate notes due June 2021 350 349 347 — — — 3.150% notes due June 2021 400 399 400 — — — 3.375% notes due November 2021 500 489 503 500 493 516 2.875% notes due December 2021 750 735 748 750 741 760 2.875% notes due March 2022 1,100 1,051 1,091 1,100 1,054 1,114 3.350% notes due July 2022 1,000 997 1,005 1,000 996 1,033 2.375% notes due October 2022 900 894 872 900 893 891 0.000% notes due November 2022 15 12 13 15 12 12 2.750% notes due February 2023 625 602 611 625 606 626 2.875% notes due March 2023 750 750 739 750 762 759 3.500% notes due June 2023 750 746 756 — — — 3.500% notes due February 2024 750 745 755 — — — 3.750% notes due July 2025 2,000 1,989 2,025 2,000 1,987 2,108 3.700% notes due December 2025 300 298 303 — — — 3.100% notes due March 2026 1,000 995 965 1,000 995 1,007 3.450% notes due January 2027 750 746 742 750 745 776 3.375% notes due April 2027 625 619 611 625 618 642 2.950% notes due October 2027 950 938 898 950 937 947 3.850% notes due June 2028 1,150 1,142 1,163 — — — 3.875% notes due December 2028 850 842 861 — — — 4.625% notes due July 2035 1,000 992 1,060 1,000 991 1,165 5.800% notes due March 2036 850 838 1,003 850 837 1,105 6.500% notes due June 2037 500 492 638 500 491 698 6.625% notes due November 2037 650 641 841 650 641 923 6.875% notes due February 2038 1,100 1,076 1,437 1,100 1,075 1,596 5.700% notes due October 2040 300 296 355 300 296 389 5.950% notes due February 2041 350 345 426 350 345 466 4.625% notes due November 2041 600 588 627 600 588 685 4.375% notes due March 2042 502 484 503 502 483 555 3.950% notes due October 2042 625 607 596 625 607 650 4.250% notes due March 2043 750 734 744 750 734 822 4.750% notes due July 2045 2,000 1,973 2,116 2,000 1,972 2,362 4.200% notes due January 2047 750 738 745 750 738 808 4.250% notes due April 2047 725 717 719 725 717 798 3.750% notes due October 2047 950 933 869 950 933 969 4.250% notes due June 2048 1,350 1,329 1,349 — — — 4.450% notes due December 2048 1,100 1,087 1,132 — — — Total commercial paper and long-term debt $ 35,667 $ 35,234 $ 36,591 $ 31,417 $ 31,067 $ 34,029 The Company’s long-term debt obligations also included $1.3 billion and $625 million of other financing obligations, of which $229 million and $107 million were current as of December 31, 2018 and 2017 , respectively. Maturities of long-term debt for the years ending December 31 are as follows: (in millions) 2019 $ 1,973 2020 3,350 2021 3,350 2022 3,215 2023 2,325 Thereafter 22,775 Commercial Paper and Revolving Bank Credit Facilities Commercial paper consists of short-duration, senior unsecured debt privately placed on a discount basis through broker-dealers. The Company has $3.5 billion five-year, $3.5 billion three-year and $3.0 billion 364-day revolving bank credit facilities with 26 banks, which mature in December 2023 , December 2021 and December 2019 , respectively. These facilities provide liquidity support for the Company’s commercial paper program and are available for general corporate purposes. As of December 31, 2018 , no amounts had been drawn on any of the bank credit facilities. The annual interest rates, which are variable based on term, are calculated based on the London Interbank Offered Rate (LIBOR) plus a credit spread based on the Company’s senior unsecured credit ratings. If amounts had been drawn on the bank credit facilities as of December 31, 2018 , annual interest rates would have ranged from 3.2% to 3.6% . Debt Covenants The Company’s bank credit facilities contain various covenants, including requiring the Company to maintain a debt to debt-plus-shareholders’ equity ratio of not more than 60% . The Company was in compliance with its debt covenants as of December 31, 2018 .

Income Taxes (Notes)

Income Taxes (Notes)	12 Months Ended
	Dec. 31, 2018
Income Tax Examination [Line Items]
Income Tax Disclosure [Text Block]	Income Taxes The current income tax provision reflects the tax consequences of revenues and expenses currently taxable or deductible on various income tax returns for the year reported. The deferred income tax provision or benefit generally reflects the net change in deferred income tax assets and liabilities during the year, excluding any deferred income tax assets and liabilities of acquired businesses. The components of the provision for income taxes for the years ended December 31 are as follows: (in millions) 2018 2017 2016 Current Provision: Federal $ 2,897 $ 3,597 $ 4,302 State and local 219 314 312 Foreign 404 254 95 Total current provision 3,520 4,165 4,709 Deferred provision (benefit) 42 (965 ) 81 Total provision for income taxes $ 3,562 $ 3,200 $ 4,790 The reconciliation of the tax provision at the U.S. federal statutory rate to the provision for income taxes and the effective tax rate for the years ended December 31 is as follows: (in millions, except percentages) 2018 2017 2016 Tax provision at the U.S. federal statutory rate $ 3,348 21.0 % $ 4,908 35.0 % $ 4,152 35.0 % Change in tax law — — (1,199 ) (8.6 ) — — State income taxes, net of federal benefit 168 1.0 197 1.4 205 1.7 Share-based awards - excess tax benefit (161 ) (1.0 ) (319 ) (2.3 ) (158 ) (1.3 ) Non-deductible compensation 117 0.7 175 1.3 128 1.1 Health insurance industry tax 552 3.5 — — 645 5.4 Foreign rate differential (203 ) (1.3 ) (282 ) (2.0 ) (105 ) (0.9 ) Other, net (259 ) (1.6 ) (280 ) (2.0 ) (77 ) (0.6 ) Provision for income taxes $ 3,562 22.3 % $ 3,200 22.8 % $ 4,790 40.4 % Deferred income tax assets and liabilities are recognized for the differences between the financial and income tax reporting bases of assets and liabilities based on enacted tax rates and laws. The components of deferred income tax assets and liabilities as of December 31 are as follows: (in millions) 2018 2017 Deferred income tax assets: Accrued expenses and allowances $ 551 $ 544 U.S. federal and state net operating loss carryforwards 190 216 Share-based compensation 91 97 Nondeductible liabilities 184 169 Non-U.S. tax loss carryforwards 426 445 Other-domestic 306 167 Other-non-U.S. 337 198 Subtotal 2,085 1,836 Less: valuation allowances (84 ) (64 ) Total deferred income tax assets 2,001 1,772 Deferred income tax liabilities: U.S. federal and state intangible assets (2,131 ) (1,998 ) Non-U.S. goodwill and intangible assets (709 ) (602 ) Capitalized software (603 ) (530 ) Depreciation and amortization (266 ) (236 ) Prepaid expenses (152 ) (223 ) Outside basis in partnerships (300 ) (279 ) Other-non-U.S. (314 ) (86 ) Total deferred income tax liabilities (4,475 ) (3,954 ) Net deferred income tax liabilities $ (2,474 ) $ (2,182 ) Valuation allowances are provided when it is considered more likely than not that deferred tax assets will not be realized. The valuation allowances primarily relate to future tax benefits on certain federal, state and non-U.S. net operating loss carryforwards. Federal net operating loss carryforwards of $99 million expire beginning in 2022 through 2037 and $17 million have an indefinite carryforward period; state net operating loss carryforwards expire beginning in 2019 through 2038. Substantially all of the non-U.S. tax loss carryforwards have indefinite carryforward periods. As of December 31, 2018 , the Company’s undistributed earnings from non-U.S. subsidiaries are intended to be indefinitely reinvested in non-U.S. operations, and therefore no U.S. deferred taxes have been recorded. Taxes payable on the remittance of such earnings would be minimal. A reconciliation of the beginning and ending amount of unrecognized tax benefits as of December 31 is as follows: (in millions) 2018 2017 2016 Gross unrecognized tax benefits, beginning of period $ 598 $ 263 $ 224 Gross increases: Current year tax positions 487 356 37 Prior year tax positions 87 40 24 Gross decreases: Prior year tax positions (84 ) (33 ) (4 ) Settlements (20 ) (24 ) (6 ) Statute of limitations lapses (12 ) (4 ) (12 ) Gross unrecognized tax benefits, end of period $ 1,056 $ 598 $ 263 The Company believes it is reasonably possible that its liability for unrecognized tax benefits will decrease in the next twelve months by $118 million as a result of audit settlements and the expiration of statutes of limitations. The Company classifies interest and penalties associated with uncertain income tax positions as income taxes within its Consolidated Statements of Operations. During the years ended December 31, 2018 , 2017 and 2016 , the Company recognized $6 million , $14 million and $11 million of interest and penalties, respectively. The Company had $95 million and $84 million of accrued interest and penalties for uncertain tax positions as of December 31, 2018 and 2017 , respectively. These amounts are not included in the reconciliation above. As of December 31, 2018 , there were $716 million of unrecognized tax benefits that, if recognized, would affect the effective tax rate. The Company currently files income tax returns in the United States, various states and localities and non-U.S. jurisdictions. The U.S. Internal Revenue Service (IRS) has completed exams on the consolidated income tax returns for fiscal years 2016 and prior. The Company’s 2018 and 2017 tax years are under review by the IRS under its Compliance Assurance Program. With the exception of a few states, the Company is no longer subject to income tax examinations prior to the 2012 tax year. In general, the Company is subject to examination in non-U.S. jurisdictions for years 2013 and forward.

Shareholders' Equity (Notes)

Shareholders' Equity (Notes)	12 Months Ended
	Dec. 31, 2018
Shareholders' Equity [Abstract]
Stockholders' Equity Note Disclosure [Text Block]	Shareholders' Equity Regulatory Capital and Dividend Restrictions The Company’s regulated insurance and HMO subsidiaries in the United States are subject to regulations and standards in their respective jurisdictions. These standards, among other things, require these subsidiaries to maintain specified levels of statutory capital, as defined by each jurisdiction, and restrict the timing and amount of dividends and other distributions that may be paid to their parent companies. In the United States, most of these regulations and standards are generally consistent with model regulations established by the National Association of Insurance Commissioners. These standards generally permit dividends to be paid from statutory unassigned surplus of the regulated subsidiary and are limited based on the regulated subsidiary’s level of statutory net income and statutory capital and surplus. These dividends are referred to as “ordinary dividends” and generally may be paid without prior regulatory approval. If the dividend, together with other dividends paid within the preceding twelve months, exceeds a specified statutory limit or is paid from sources other than earned surplus, it is generally considered an “extraordinary dividend” and must receive prior regulatory approval. For both the years ended December 31, 2018 and 2017 , the Company’s regulated subsidiaries paid their parent companies dividends of $3.7 billion , including $1.1 billion of extraordinary dividends. The Company's regulated subsidiaries had estimated aggregate statutory capital and surplus of $23.7 billion as of December 31, 2018 . The estimated statutory capital and surplus necessary to satisfy regulatory requirements of the Company's regulated subsidiaries was approximately $10.3 billion as of December 31, 2018 . Optum Bank must meet minimum capital requirements of the Federal Deposit Insurance Corporation (FDIC) to be considered “Well Capitalized” under the capital adequacy rules to which it is subject. At December 31, 2018 , the Company believes that Optum Bank met the FDIC requirements to be considered “Well Capitalized.” Share Repurchase Program Under its Board of Directors’ authorization, the Company maintains a share repurchase program. The objectives of the share repurchase program are to optimize the Company’s capital structure and cost of capital, thereby improving returns to shareholders, as well as to offset the dilutive impact of share-based awards. Repurchases may be made from time to time in open market purchases or other types of transactions (including prepaid or structured share repurchase programs), subject to certain Board restrictions. In June 2018, the Board renewed the Company’s share repurchase program with an authorization to repurchase up to 100 million shares of its common stock. A summary of common share repurchases for the years ended December 31, 2018 and 2017 is as follows: Years Ended December 31, (in millions, except per share data) 2018 2017 Common share repurchases, shares 19 9 Common share repurchases, average price per share $ 236.72 $ 173.54 Common share repurchases, aggregate cost $ 4,500 $ 1,500 Board authorized shares remaining 94 42 Dividends In June 2018, the Company’s Board of Directors increased the Company’s annual dividend rate to shareholders to $3.60 per share compared to $3.00 per share, which the Company had paid since June 2017. Declaration and payment of future quarterly dividends is at the discretion of the Board and may be adjusted as business needs or market conditions change.

Share-Based Compensation (Notes

Share-Based Compensation (Notes)	12 Months Ended
	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Disclosure of Compensation Related Costs, Share-based Payments [Text Block]	Share-Based Compensation The Company’s outstanding share-based awards consist mainly of non-qualified stock options, SARs and restricted shares. As of December 31, 2018 , the Company had 42 million shares available for future grants of share-based awards under the Plan. As of December 31, 2018 , there were also 7 million shares of common stock available for issuance under the ESPP. Stock Options and SARs Stock option and SAR activity for the year ended December 31, 2018 is summarized in the table below: Shares Weighted- Average Exercise Price Weighted- Average Remaining Contractual Life Aggregate Intrinsic Value (in millions) (in years) (in millions) Outstanding at beginning of period 37 $ 102 Granted 7 229 Exercised (8 ) 78 Forfeited (1 ) 162 Outstanding at end of period 35 131 6.5 $ 4,114 Exercisable at end of period 16 87 5.0 2,560 Vested and expected to vest, end of period 34 129 6.5 4,072 Restricted Shares Restricted share activity for the year ended December 31, 2018 is summarized in the table below: (shares in millions) Shares Weighted-Average Grant Date Fair Value per Share Nonvested at beginning of period 7 $ 128 Granted 2 229 Vested (3 ) 119 Nonvested at end of period 6 163 Other Share-Based Compensation Data (in millions, except per share amounts) For the Years Ended December 31, 2018 2017 2016 Stock Options and SARs Weighted-average grant date fair value of shares granted, per share $ 43 $ 29 $ 20 Total intrinsic value of stock options and SARs exercised 1,431 1,473 595 Restricted Shares Weighted-average grant date fair value of shares granted, per share 229 163 115 Total fair value of restricted shares vested $ 521 $ 460 $ 274 Employee Stock Purchase Plan Number of shares purchased 2 2 2 Share-Based Compensation Items Share-based compensation expense, before tax $ 638 $ 597 $ 485 Share-based compensation expense, net of tax effects 587 531 417 Income tax benefit realized from share-based award exercises 239 431 236 (in millions, except years) December 31, 2018 Unrecognized compensation expense related to share awards $ 628 Weighted-average years to recognize compensation expense 1.3 Share-Based Compensation Recognition and Estimates The principal assumptions the Company used in calculating grant-date fair value for stock options and SARs were as follows: For the Years Ended December 31, 2018 2017 2016 Risk-free interest rate 2.6% - 3.1% 1.9% - 2.1% 1.2% - 1.4% Expected volatility 18.7% - 19.3% 18.5% - 20.7% 20.8% - 22.5% Expected dividend yield 1.3% - 1.5% 1.4% - 1.6% 1.8% Forfeiture rate 5.0% 5.0% 5.0% Expected life in years 5.6 5.7 5.6 - 5.9 Risk-free interest rates are based on U.S. Treasury yields in effect at the time of grant. Expected volatilities are based on the historical volatility of the Company’s common stock and the implied volatility from exchange-traded options on the Company’s common stock. Expected dividend yields are based on the per share cash dividend paid by the Company. The Company uses historical data to estimate option and SAR exercises and forfeitures within the valuation model. The expected lives of options and SARs granted represents the period of time that the awards granted are expected to be outstanding based on historical exercise patterns. Other Employee Benefit Plans The Company offers a 401(k) plan for its employees. Compensation expense related to this plan was not material for 2018, 2017 and 2016. In addition, the Company maintains non-qualified, deferred compensation plans, which allow certain members of senior management and executives to defer portions of their salary or bonus and receive certain Company contributions on such deferrals, subject to plan limitations. The deferrals are recorded within long-term investments with an approximately equal amount in other liabilities in the Consolidated Balance Sheets. The total deferrals are distributable based upon termination of employment or other periods, as elected under each plan and were $988 million and $865 million as of December 31, 2018 and 2017 , respectively.

Commitments and Contingencies (

Commitments and Contingencies (Notes)	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies Disclosure [Text Block]	Commitments and Contingencies The Company leases facilities and equipment under long-term operating leases that are non-cancelable and expire on various dates. Rent expense under all operating leases for the years ended December 31, 2018 , 2017 and 2016 was $751 million , $710 million and $608 million , respectively. As of December 31, 2018 , future minimum annual lease payments, net of sublease income, under all non-cancelable operating leases were as follows: (in millions) Future Minimum Lease Payments 2019 $ 669 2020 592 2021 511 2022 423 2023 338 Thereafter 1,343 The Company provides guarantees related to its service level under certain contracts. If minimum standards are not met, the Company may be financially at risk up to a stated percentage of the contracted fee or a stated dollar amount. None of the amounts accrued, paid or charged to income for service level guarantees were material as of December 31, 2018 , 2017 or 2016 . As of December 31, 2018 , the Company had outstanding, undrawn letters of credit with financial institutions of $83 million and surety bonds outstanding with insurance companies of $1.3 billion , primarily to bond contractual performance. Pending Acquisition In December 2017, the Company entered into an agreement to acquire a company in the health care sector for a total of approximately $4.3 billion . Legal Matters Because of the nature of its businesses, the Company is frequently made party to a variety of legal actions and regulatory inquiries, including class actions and suits brought by members, care providers, consumer advocacy organizations, customers and regulators, relating to the Company’s businesses, including management and administration of health benefit plans and other services. These matters include medical malpractice, employment, intellectual property, antitrust, privacy and contract claims and claims related to health care benefits coverage and other business practices. The Company records liabilities for its estimates of probable costs resulting from these matters where appropriate. Estimates of costs resulting from legal and regulatory matters involving the Company are inherently difficult to predict, particularly where the matters: involve indeterminate claims for monetary damages or may involve fines, penalties or punitive damages; present novel legal theories or represent a shift in regulatory policy; involve a large number of claimants or regulatory bodies; are in the early stages of the proceedings; or could result in a change in business practices. Accordingly, the Company is often unable to estimate the losses or ranges of losses for those matters where there is a reasonable possibility or it is probable that a loss may be incurred. Government Investigations, Audits and Reviews The Company has been involved or is currently involved in various governmental investigations, audits and reviews. These include routine, regular and special investigations, audits and reviews by CMS, state insurance and health and welfare departments, state attorneys general, the Office of the Inspector General, the Office of Personnel Management, the Office of Civil Rights, the Government Accountability Office, the Federal Trade Commission, U.S. Congressional committees, the U.S. Department of Justice, the SEC, the Internal Revenue Service, the U.S. Drug Enforcement Administration, the U.S. Department of Labor, the Federal Deposit Insurance Corporation, the Defense Contract Audit Agency and other governmental authorities. Similarly, our international businesses are also subject to investigations, audits and reviews by applicable foreign governments, including South American and other non-U.S. governmental authorities. Certain of the Company’s businesses have been reviewed or are currently under review, including for, among other matters, compliance with coding and other requirements under the Medicare risk-adjustment model. CMS has selected certain of the Company’s local plans for risk adjustment data validation (RADV) audits to validate the coding practices of and supporting documentation maintained by health care providers and such audits may result in retrospective adjustments to payments made to the Company’s health plans. On February 14, 2017, the Department of Justice (DOJ) announced its decision to pursue certain claims within a lawsuit initially asserted against the Company and filed under seal by a whistleblower in 2011. The whistleblower’s complaint, which was unsealed on February 15, 2017, alleges that the Company made improper risk adjustment submissions and violated the False Claims Act. On February 12, 2018, the court granted in part and denied in part the Company’s motion to dismiss. In May 2018, DOJ moved to dismiss the Company’s counterclaims, which were filed in March 2018, and moved for partial summary judgment. Those motions were argued in September 2018. The Company cannot reasonably estimate the outcome that may result from this matter given its procedural status.

Segment Financial Information (

Segment Financial Information (Notes)	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
Segment Financial Information [Text Block]	Segment Financial Information Factors used to determine the Company’s reportable segments include the nature of operating activities, economic characteristics, existence of separate senior management teams and the type of information used by the Company’s chief operating decision maker to evaluate its results of operations. Reportable segments with similar economic characteristics, products and services, customers, distribution methods and operational processes that operate in a similar regulatory environment are combined. The following is a description of the types of products and services from which each of the Company’s four reportable segments derives its revenues: • UnitedHealthcare includes the combined results of operations of UnitedHealthcare Employer & Individual, UnitedHealthcare Medicare & Retirement, UnitedHealthcare Community & State and UnitedHealthcare Global. The U.S. businesses share significant common assets, including a contracted network of physicians, health care professionals, hospitals and other facilities, information technology and consumer engagement infrastructure and other resources. UnitedHealthcare Employer & Individual offers an array of consumer-oriented health benefit plans and services for large national employers, public sector employers, mid-sized employers, small businesses and individuals nationwide. UnitedHealthcare Medicare & Retirement provides health care coverage and health and well-being services to individuals age 50 and older, addressing their unique needs for preventive and acute health care services as well as services dealing with chronic disease and other specialized issues for older individuals. UnitedHealthcare Community & State’s primary customers oversee Medicaid plans, the Children’s Health Insurance Program and other federal, state and community health care programs. UnitedHealthcare Global is a diversified global health services business with a variety of offerings, including international commercial health and dental benefits and health care delivery. • OptumHealth focuses on care delivery, care management, wellness and consumer engagement, and health financial services. OptumHealth serves the physical, emotional and health-related financial needs of individuals, enabling population health through programs offered by employers, payers, government entities and directly with the care delivery system. OptumHealth offers access to networks of care provider specialists, health management services, care delivery, consumer engagement and financial services. • OptumInsight provides services, technology and health care expertise to major participants in the health care industry. Hospital systems, physicians, health plans, governments, life sciences companies and other organizations that comprise the health care industry depend on OptumInsight to help them improve performance, achieve efficiency, reduce costs, meet compliance mandates and modernize their core operating systems to meet the changing needs of the health system. • OptumRx offers pharmacy care services and programs, including retail network contracting, home delivery, specialty and compounding pharmacy services, purchasing and clinical capabilities, and develops programs in areas such as step therapy, formulary management, drug adherence and disease/drug therapy management. The Company’s accounting policies for reportable segment operations are consistent with those described in the Summary of Significant Accounting Policies (see Note 2 ). Transactions between reportable segments principally consist of sales of pharmacy care products and services to UnitedHealthcare customers by OptumRx, certain product offerings and care management and local care delivery services sold to UnitedHealthcare by OptumHealth, and health information and technology solutions, consulting and other services sold to UnitedHealthcare by OptumInsight. These transactions are recorded at management’s estimate of fair value. Intersegment transactions are eliminated in consolidation. Assets and liabilities that are jointly used are assigned to each reportable segment using estimates of pro-rata usage. Cash and investments are assigned such that each reportable segment has working capital and/or at least minimum specified levels of regulatory capital. As a percentage of the Company’s total consolidated revenues, premium revenues from CMS were 30% , 28% and 25% for 2018 , 2017 and 2016 , respectively, most of which were generated by UnitedHealthcare Medicare & Retirement and included in the UnitedHealthcare segment. U.S. customer revenue represented approximately 96% , 96% and 97% of consolidated total revenues for 2018 , 2017 and 2016 , respectively. Long-lived fixed assets located in the United States represented approximately 76% and 77% of the total long-lived fixed assets as of December 31, 2018 and 2017 , respectively. The non-U.S. revenues and fixed assets are primarily related to UnitedHealthcare Global. The following table presents the reportable segment financial information: Optum (in millions) UnitedHealthcare OptumHealth OptumInsight OptumRx Optum Eliminations Optum Corporate and Eliminations Consolidated 2018 Revenues - unaffiliated customers: Premiums $ 174,282 $ 3,805 $ — $ — $ — $ 3,805 $ — $ 178,087 Products — 52 111 29,438 — 29,601 — 29,601 Services 8,366 4,925 3,280 612 — 8,817 — 17,183 Total revenues - unaffiliated customers 182,648 8,782 3,391 30,050 — 42,223 — 224,871 Total revenues - affiliated customers — 14,882 5,596 39,440 (1,409 ) 58,509 (58,509 ) — Investment and other income 828 481 21 46 — 548 — 1,376 Total revenues $ 183,476 $ 24,145 $ 9,008 $ 69,536 $ (1,409 ) $ 101,280 $ (58,509 ) $ 226,247 Earnings from operations $ 9,113 $ 2,430 $ 2,243 $ 3,558 $ — $ 8,231 $ — $ 17,344 Interest expense — — — — — — (1,400 ) (1,400 ) Earnings before income taxes $ 9,113 $ 2,430 $ 2,243 $ 3,558 $ — $ 8,231 $ (1,400 ) $ 15,944 Total assets $ 82,938 $ 29,837 $ 11,039 $ 33,912 $ — $ 74,788 $ (5,505 ) $ 152,221 Purchases of property, equipment and capitalized software 761 593 517 192 — 1,302 — 2,063 Depreciation and amortization 845 439 654 490 — 1,583 — 2,428 2017 Revenues - unaffiliated customers: Premiums $ 154,709 $ 3,744 $ — $ — $ — $ 3,744 $ — $ 158,453 Products — 44 106 26,216 — 26,366 — 26,366 Services 7,890 4,013 2,849 565 — 7,427 — 15,317 Total revenues - unaffiliated customers 162,599 7,801 2,955 26,781 — 37,537 — 200,136 Total revenues - affiliated customers — 12,429 5,127 36,954 (1,227 ) 53,283 (53,283 ) — Investment and other income 658 340 5 20 — 365 — 1,023 Total revenues $ 163,257 $ 20,570 $ 8,087 $ 63,755 $ (1,227 ) $ 91,185 $ (53,283 ) $ 201,159 Earnings from operations $ 8,498 $ 1,823 $ 1,770 $ 3,118 $ — $ 6,711 $ — $ 15,209 Interest expense — — — — — — (1,186 ) (1,186 ) Earnings before income taxes $ 8,498 $ 1,823 $ 1,770 $ 3,118 $ — $ 6,711 $ (1,186 ) $ 14,023 Total assets $ 76,676 $ 26,931 $ 11,273 $ 29,551 $ — $ 67,755 $ (5,373 ) $ 139,058 Purchases of property, equipment and capitalized software 737 510 588 188 — 1,286 — 2,023 Depreciation and amortization 758 380 614 493 — 1,487 — 2,245 2016 Revenues - unaffiliated customers: Premiums $ 140,455 $ 3,663 $ — $ — $ — $ 3,663 $ — $ 144,118 Products 1 48 103 26,506 — 26,657 — 26,658 Services 7,514 2,498 2,670 554 — 5,722 — 13,236 Total revenues - unaffiliated customers 147,970 6,209 2,773 27,060 — 36,042 — 184,012 Total revenues - affiliated customers — 10,491 4,559 33,372 (1,088 ) 47,334 (47,334 ) — Investment and other income 611 208 1 8 — 217 — 828 Total revenues $ 148,581 $ 16,908 $ 7,333 $ 60,440 $ (1,088 ) $ 83,593 $ (47,334 ) $ 184,840 Earnings from operations $ 7,307 $ 1,428 $ 1,513 $ 2,682 $ — $ 5,623 $ — $ 12,930 Interest expense — — — — — — (1,067 ) (1,067 ) Earnings before income taxes $ 7,307 $ 1,428 $ 1,513 $ 2,682 $ — $ 5,623 $ (1,067 ) $ 11,863 Total assets $ 70,505 $ 18,656 $ 9,017 $ 29,066 $ — $ 56,739 $ (4,434 ) $ 122,810 Purchases of property, equipment and capitalized software 640 345 571 149 — 1,065 — 1,705 Depreciation and amortization 724 297 559 475 — 1,331 — 2,055

Quarterly Financial Data (Unaud

Quarterly Financial Data (Unaudited) (Notes)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information [Text Block]	Quarterly Financial Data (Unaudited) Selected quarterly financial information for all quarters of 2018 and 2017 is as follows: For the Quarter Ended (in millions, except per share data) March 31 June 30 September 30 December 31 2018 Revenues $ 55,188 $ 56,086 $ 56,556 $ 58,417 Operating costs 51,135 51,882 51,966 53,920 Earnings from operations 4,053 4,204 4,590 4,497 Net earnings 2,924 3,010 3,284 3,164 Net earnings attributable to UnitedHealth Group common shareholders 2,836 2,922 3,188 3,040 Net earnings per share attributable to UnitedHealth Group common shareholders: Basic 2.94 3.04 3.31 3.16 Diluted 2.87 2.98 3.24 3.10 2017 Revenues $ 48,723 $ 50,053 $ 50,322 $ 52,061 Operating costs 45,310 46,322 46,234 48,084 Earnings from operations 3,413 3,731 4,088 3,977 Net earnings 2,191 2,350 2,561 3,721 Net earnings attributable to UnitedHealth Group common shareholders 2,172 2,284 2,485 3,617 Net earnings per share attributable to UnitedHealth Group common shareholders: Basic 2.28 2.37 2.57 3.73 Diluted 2.23 2.32 2.51 3.65

Schedule I (Notes)

Schedule I (Notes)	12 Months Ended
	Dec. 31, 2018
Condensed Statement of Income Captions [Line Items]
Condensed Financial Information of Parent Company Only Disclosure [Text Block]	Schedule I Condensed Financial Information of Registrant (Parent Company Only) UnitedHealth Group Condensed Balance Sheets (in millions, except per share data) December 31, December 31, Assets Current assets: Cash and cash equivalents $ 434 $ 359 Other current assets 197 575 Total current assets 631 934 Equity in net assets of subsidiaries 83,244 76,231 Long-term notes receivable from subsidiaries 4,461 4,278 Other assets 972 839 Total assets $ 89,308 $ 82,282 Liabilities and shareholders’ equity Current liabilities: Accounts payable and accrued liabilities $ 618 $ 502 Current portion of notes payable to subsidiaries 714 466 Commercial paper and current maturities of long-term debt 1,744 2,749 Total current liabilities 3,076 3,717 Long-term debt, less current maturities 33,490 28,318 Long-term notes payable to subsidiaries 560 1,518 Other liabilities 486 953 Total liabilities 37,612 34,506 Commitments and contingencies (Note 4) Shareholders’ equity: Preferred stock, $0.001 par value -10 shares authorized; no shares issued or outstanding — — Common stock, $0.01 par value - 3,000 shares authorized; 960 and 969 issued and outstanding 10 10 Additional paid-in capital — 1,703 Retained earnings 55,846 48,730 Accumulated other comprehensive loss (4,160 ) (2,667 ) Total UnitedHealth Group shareholders’ equity 51,696 47,776 Total liabilities and shareholders’ equity $ 89,308 $ 82,282 See Notes to the Condensed Financial Statements of Registrant Schedule I Condensed Financial Information of Registrant (Parent Company Only) UnitedHealth Group Condensed Statements of Comprehensive Income For the Years Ended December 31, (in millions) 2018 2017 2016 Revenues: Investment and other income $ 194 $ 527 $ 522 Total revenues 194 527 522 Operating costs: Operating costs 35 — (22 ) Interest expense 1,285 1,114 995 Total operating costs 1,320 1,114 973 Loss before income taxes (1,126 ) (587 ) (451 ) Benefit for income taxes 251 214 165 Loss of parent company (875 ) (373 ) (286 ) Equity in undistributed income of subsidiaries 12,861 10,931 7,303 Net earnings 11,986 10,558 7,017 Other comprehensive (loss) income (1,517 ) 14 653 Comprehensive income $ 10,469 $ 10,572 $ 7,670 See Notes to the Condensed Financial Statements of Registrant Schedule I Condensed Financial Information of Registrant (Parent Company Only) UnitedHealth Group Condensed Statements of Cash Flows For the Years Ended December 31, (in millions) 2018 2017 2016 Operating activities Cash flows from operating activities $ 6,099 $ 2,021 $ 4,294 Investing activities Issuances of notes to subsidiaries (1,420 ) — (824 ) Repayments of notes to subsidiaries 1,419 2,071 — Cash paid for acquisitions (4,066 ) (2,313 ) (2,292 ) Return of capital to parent company 4,196 3,375 2,143 Capital contributions to subsidiaries (1,259 ) (959 ) (765 ) Other, net 4 — 168 Cash flows (used for) from investing activities (1,126 ) 2,174 (1,570 ) Financing activities Common stock repurchases (4,500 ) (1,500 ) (1,280 ) Proceeds from common stock issuances 838 688 429 Cash dividends paid (3,320 ) (2,773 ) (2,261 ) Repayments of commercial paper, net (201 ) (3,508 ) (382 ) Proceeds from issuance of long-term debt 6,935 5,291 3,968 Repayments of long-term debt (2,600 ) (3,472 ) (2,596 ) (Repayments) proceeds of notes from subsidiary (1,127 ) 1,704 (30 ) Other, net (923 ) (446 ) (421 ) Cash flows used for financing activities (4,898 ) (4,016 ) (2,573 ) Increase in cash and cash equivalents 75 179 151 Cash and cash equivalents, beginning of period 359 180 29 Cash and cash equivalents, end of period $ 434 $ 359 $ 180 Supplemental cash flow disclosures Cash paid for interest $ 1,294 $ 1,062 $ 974 Cash paid for income taxes 2,379 3,455 4,557 Supplemental schedule of non-cash investing activities Common stock issued for acquisitions $ — $ 2,164 $ — Conversion of note receivable from subsidiaries to equity — 4,378 — See Notes to the Condensed Financial Statements of Registrant Schedule I Condensed Financial Information of Registrant (Parent Company Only) UnitedHealth Group Notes to Condensed Financial Statements 1. Basis of Presentation UnitedHealth Group’s parent company financial information has been derived from its consolidated financial statements and should be read in conjunction with the consolidated financial statements included in this Form 10-K. The accounting policies for the registrant are the same as those described in Note 2 of Notes to the Consolidated Financial Statements included in Part II, Item 8, “Financial Statements and Supplementary Data.” 2. Subsidiary Transactions Investment in Subsidiaries. UnitedHealth Group’s investment in subsidiaries is stated at cost plus equity in undistributed earnings of subsidiaries. Dividends and Capital Distributions. Cash dividends received from subsidiaries and included in Cash Flows from Operating Activities in the Condensed Statements of Cash Flows were $5.6 billion , $3.4 billion and $3.7 billion in 2018, 2017 and 2016, respectively. Additionally, $4.2 billion , $3.4 billion and $2.1 billion in cash were received as a return of capital to the parent company during 2018, 2017 and 2016, respectively. 3. Commercial Paper and Long-Term Debt Discussion of commercial paper and long-term debt can be found in Note 8 of Notes to the Consolidated Financial Statements included in Part II, Item 8, “Financial Statements and Supplementary Data.” Long-term debt obligations of the parent company do not include other financing obligations at subsidiaries that totaled $1.3 billion and $625 million at December 31, 2018 and 2017, respectively. Maturities of commercial paper and long-term debt for the years ending December 31 are as follows: (in millions) 2019 $ 1,750 2020 3,150 2021 3,150 2022 3,015 2023 2,125 Thereafter 22,477 4. Commitments and Contingencies For a summary of commitments and contingencies, see Note 12 of Notes to the Consolidated Financial Statements included in Part II, Item 8, “Financial Statements and Supplementary Data.”

Basis of Presentation, Uses o_2

Basis of Presentation, Uses of Estimates and Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2018
Basis of Accounting, Policy [Policy Text Block]	Basis of Presentation The Company has prepared the Consolidated Financial Statements according to U.S. Generally Accepted Accounting Principles (GAAP) and has included the accounts of UnitedHealth Group and its subsidiaries.
Use of Estimates, Policy [Policy Text Block]	Use of Estimates These Consolidated Financial Statements include certain amounts based on the Company’s best estimates and judgments. The Company’s most significant estimates relate to estimates and judgments for medical costs payable and revenues, valuation and impairment analysis of goodwill and other intangible assets and estimates of other current liabilities and other current receivables. Certain of these estimates require the application of complex assumptions and judgments, often because they involve matters that are inherently uncertain and will likely change in subsequent periods. The impact of any change in estimates is included in earnings in the period in which the estimate is adjusted.
Revenue Recognition, Policy [Policy Text Block]	Revenues Premiums Premium revenues are primarily derived from risk-based health insurance arrangements in which the premium is typically at a fixed rate per individual served for a one-year period, and the Company assumes the economic risk of funding its customers’ health care and related administrative costs. Premium revenues are recognized in the period in which eligible individuals are entitled to receive health care benefits. Health care premium payments received from the Company’s customers in advance of the service period are recorded as unearned revenues. Fully insured commercial products of U.S. health plans, Medicare Advantage and Medicare Prescription Drug Benefit (Medicare Part D) plans with medical loss ratios as calculated under the definitions in the Patient Protection and Affordable Care Act (ACA) and related federal and state regulations and implementing regulation, that fall below certain targets are required to rebate ratable portions of their premiums annually. Medicare Advantage premium revenue includes the impact of the Centers for Medicare & Medicaid Services (CMS) quality bonuses based on plans’ Star ratings. Premium revenues are recognized based on the estimated premiums earned, net of projected rebates, because the Company is able to reasonably estimate the ultimate premiums of these contracts. The Company also records premium revenues from capitation arrangements at its OptumHealth businesses. The Company’s Medicare Advantage and Medicare Part D premium revenues are subject to periodic adjustment under CMS’ risk adjustment payment methodology. CMS deploys a risk adjustment model that apportions premiums paid to all health plans according to health severity and certain demographic factors. The CMS risk adjustment model provides higher per member payments for enrollees diagnosed with certain conditions and lower payments for enrollees who are healthier. Under this risk adjustment methodology, CMS calculates the risk adjusted premium payment using diagnosis data from hospital inpatient, hospital outpatient and physician treatment settings. The Company and health care providers collect, capture and submit the necessary and available diagnosis data to CMS within prescribed deadlines. The Company estimates risk adjustment premium revenues based upon the diagnosis data submitted and expected to be submitted to CMS. Risk adjustment data for the Company’s plans are subject to review by the government, including audit by regulators. See Note 12 for additional information regarding these audits. Products and Services For the Company’s OptumRx pharmacy care services business, the majority of revenues are derived from products sold through a contracted network of retail pharmacies or home delivery, specialty and compounding pharmacy facilities. Product revenues include ingredient costs (net of rebates), a negotiated dispensing fee and customer co-payments for drugs dispensed through the Company’s mail-service pharmacy. In retail pharmacy transactions, revenues recognized exclude the member’s applicable co-payment. Pharmacy products are billed to customers based on the number of transactions occurring during the billing period. Product revenues are recognized when the prescriptions are dispensed through the retail network or received by consumers through the Company’s mail-service pharmacy. The Company has entered into contracts in which it is primarily obligated to pay its network pharmacy providers for benefits provided to their customers regardless of whether the Company is paid. The Company is also involved in establishing the prices charged by retail pharmacies, determining which drugs will be included in formulary listings and selecting which retail pharmacies will be included in the network offered to plan sponsors’ members and accordingly, are reported on a gross basis. Services revenue consists of fees derived from services performed for customers that self-insure the health care costs of their employees and employees’ dependents. Under service fee contracts, the Company receives monthly, a fixed fee per employee, which is recognized as revenue as the Company performs, or makes available, the applicable services to the customer. The customers retain the risk of financing health care costs for their employees and employees’ dependents, and the Company administers the payment of customer funds to physicians and other health care professionals from customer-funded bank accounts. As the Company has neither the obligation for funding the health care costs, nor the primary responsibility for providing the medical care, the Company does not recognize premium revenue and medical costs for these contracts in its Consolidated Financial Statements. For these fee-based customer arrangements, the Company provides coordination and facilitation of medical services; transaction processing; customer, consumer and care professional services; and access to contracted networks of physicians, hospitals and other health care professionals. These services are performed throughout the contract period. Revenues are also comprised of a number of services and products sold through Optum. OptumHealth’s service revenues include net patient service revenues that are recorded based upon established billing rates, less allowances for contractual adjustments, and are recognized as services are provided. For its financial services offerings, OptumHealth charges fees and earns investment income on managed funds. OptumInsight provides software and information products, advisory consulting arrangements and services outsourcing contracts, which may be delivered over several years. OptumInsight revenues are generally recognized over time and measured each period based on the progress to date as services are performed or made available to customers. As of December 31, 2018 and 2017 , accounts receivables related to products and services were $3.9 billion and $3.7 billion , respectively. In 2018 and 2017 , the Company had no material bad-debt expense and there were no material contract assets, contract liabilities or deferred contract costs recorded on the Consolidated Balance Sheets as of December 31, 2018 or 2017 . For the years ended December 31, 2018 and 2017 , revenue recognized from performance obligations related to prior periods (for example, due to changes in transaction price) was not material. Revenue expected to be recognized in any future year related to remaining performance obligations, excluding revenue pertaining to contracts that have an original expected duration of one year or less, contracts where revenue is recognized as invoiced and contracts with variable consideration related to undelivered performance obligations, is not material. See Note 13 for disaggregation of revenue by segment and type.
Medical Costs and Medical Costs Payable [Policy Text Block]	Medical Costs and Medical Costs Payable The Company’s estimate of medical costs payable represents management’s best estimate of its liability for unpaid medical costs as of December 31, 2018. Each period, the Company re-examines previously established medical costs payable estimates based on actual claim submissions and other changes in facts and circumstances. As more complete claim information becomes available, the Company adjusts the amount of the estimates and includes the changes in estimates in medical costs in the period in which the change is identified. Approximately 90% of claims related to medical care services are known and settled within 90 days from the date of service and substantially all within twelve months. Medical costs and medical costs payable include estimates of the Company’s obligations for medical care services that have been rendered on behalf of insured consumers, but for which claims have either not yet been received, processed, or paid. The Company develops estimates for medical care services incurred but not reported (IBNR), which includes estimates for claims that have not been received or fully processed, using an actuarial process that is consistently applied, centrally controlled and automated. The actuarial models consider factors such as time from date of service to claim processing, seasonal variances in medical care consumption, health care professional contract rate changes, medical care utilization and other medical cost trends, membership volume and demographics, the introduction of new technologies, benefit plan changes, and business mix changes related to products, customers and geography. In developing its medical costs payable estimates, the Company applies different estimation methods depending on which incurred claims are being estimated. For the most recent two months, the Company estimates claim costs incurred by applying observed medical cost trend factors to the average per member per month (PMPM) medical costs incurred in prior months for which more complete claim data are available, supplemented by a review of near-term completion factors (actuarial estimates, based upon historical experience and analysis of current trends, of the percentage of incurred claims during a given period that have been adjudicated by the Company at the date of estimation). For months prior to the most recent two months, the Company applies the completion factors to actual claims adjudicated-to-date to estimate the expected amount of ultimate incurred claims for those months.
Cost of Sales, Policy [Policy Text Block]	Cost of Products Sold The Company’s cost of products sold includes the cost of pharmaceuticals dispensed to unaffiliated customers either directly at its home delivery and specialty pharmacy locations, or indirectly through its nationwide network of participating pharmacies. Rebates attributable to non-affiliated clients are accrued as rebates receivable and a reduction of cost of products sold, with a corresponding payable for the amounts of the rebates to be remitted to those non-affiliated clients in accordance with their contracts and recorded in the Consolidated Statements of Operations as a reduction of product revenue. Cost of products sold also includes the cost of personnel to support the Company’s transaction processing services, system sales, maintenance and professional services.
Cash and Cash Equivalents, Policy [Policy Text Block]	Cash, Cash Equivalents and Investments Cash and cash equivalents are highly liquid investments that have an original maturity of three months or less. The fair value of cash and cash equivalents approximates their carrying value because of the short maturity of the instruments.
Investment, Policy [Policy Text Block]	Investments with maturities of less than one year are classified as short-term. Because of regulatory requirements, certain investments are included in long-term investments regardless of their maturity date. The Company classifies these investments as held-to-maturity and reports them at amortized cost. Substantially all other investments are classified as available-for-sale and reported at fair value based on quoted market prices, where available. Equity investments, with certain exceptions, are measured at fair value with changes in fair value recognized in net earnings. The Company excludes unrealized gains and losses on investments in available-for-sale debt securities from net earnings and reports them as comprehensive income and, net of income tax effects, as a separate component of equity. To calculate realized gains and losses on the sale of debt securities, the Company specifically identifies the cost of each investment sold. The Company evaluates an investment for impairment by considering the length of time and extent to which market value has been less than cost or amortized cost, the financial condition and near-term prospects of the issuer as well as specific events or circumstances that may influence the operations of the issuer and the Company’s intent to sell the security or the likelihood that it will be required to sell the security before recovery of the entire amortized cost. New information and the passage of time can change these judgments. The Company manages its investment portfolio to limit its exposure to any one issuer or market sector, and largely limits its investments to investment grade quality. Securities downgraded below policy minimums after purchase will be disposed of in accordance with the Company’s investment policy.
AARP Assets Under Management [Policy Text Block]	Assets Under Management The Company provides health insurance products and services to members of AARP under a Supplemental Health Insurance Program (the AARP Program) and to AARP members and non-members under separate Medicare Advantage and Medicare Part D arrangements. The products and services under the AARP Program include supplemental Medicare benefits, hospital indemnity insurance, including insurance for individuals between 50 to 64 years of age, and other related products. Pursuant to the Company’s agreement, AARP Program assets are managed separately from the Company’s general investment portfolio and are used to pay costs associated with the AARP Program. These assets are invested at the Company’s discretion, within investment guidelines approved by AARP. The Company does not guarantee any rates of return on these investments and, upon any transfer of the AARP Program contract to another entity, the Company would transfer cash equal in amount to the fair value of these investments at the date of transfer to that entity. Because the purpose of these assets is to fund the medical costs payable, the rate stabilization fund (RSF) liabilities and other related liabilities associated with this AARP contract, assets under management are classified as current assets, consistent with the classification of these liabilities. The effects of changes in other balance sheet amounts associated with the AARP Program also accrue to the overall benefit of the AARP policyholders through the RSF balance. Accordingly, the Company excludes the effect of such changes in its Consolidated Statements of Cash Flows.
Receivables, Policy [Policy Text Block]	Other Current Receivables Other current receivables include amounts due from pharmaceutical manufacturers for rebates and other miscellaneous amounts due to the Company. The Company’s pharmacy care services businesses contract with pharmaceutical manufacturers, some of which provide rebates based on use of the manufacturers’ products by its affiliated and non-affiliated clients. The Company accrues rebates as they are earned by its clients on a monthly basis based on the terms of the applicable contracts, historical data and current estimates. The pharmacy care services businesses bill these rebates to the manufacturers on a monthly or quarterly basis depending on the contractual terms and record rebates attributable to affiliated clients as a reduction to medical costs. The Company generally receives rebates two to five months after billing. As of December 31, 2018 and 2017, total pharmaceutical manufacturer rebates receivable included in other receivables in the Consolidated Balance Sheets amounted to $4.2 billion and $3.8 billion , respectively.
Property, Plant and Equipment, Policy [Policy Text Block]	Property, Equipment and Capitalized Software Property, equipment and capitalized software are stated at cost, net of accumulated depreciation and amortization. Capitalized software consists of certain costs incurred in the development of internal-use software, including external direct costs of materials and services and applicable payroll costs of employees devoted to specific software development. The Company calculates depreciation and amortization using the straight-line method over the estimated useful lives of the assets. The useful lives for property, equipment and capitalized software are: Furniture, fixtures and equipment 3 to 10 years Buildings 35 to 40 years Capitalized software 3 to 5 years Leasehold improvements are depreciated over the shorter of the remaining lease term or their estimated useful economic life.
Goodwill and Intangible Assets, Goodwill, Policy [Policy Text Block]	Goodwill To determine whether goodwill is impaired, annually or more frequently if needed, the Company performs a multi-step impairment test. The Company may first assess qualitative factors to determine if it is more likely than not that the carrying value of a reporting unit exceeds its estimated fair value. The Company may also elect to skip the qualitative testing and proceed directly to the quantitative testing. When performing quantitative testing, the Company first estimates the fair values of its reporting units using discounted cash flows. To determine fair values, the Company must make assumptions about a wide variety of internal and external factors. Significant assumptions used in the impairment analysis include financial projections of free cash flow (including significant assumptions about operations, capital requirements and income taxes), long-term growth rates for determining terminal value and discount rates. Comparative market multiples are used to corroborate the results of the discounted cash flow test. If the fair value is less than the carrying value of the reporting unit, then the implied value of goodwill would be calculated and compared to the carrying amount of goodwill to determine whether goodwill is impaired. There was no impairment of goodwill during the year ended December 31, 2018 .
Goodwill and Intangible Assets, Intangible Assets, Policy [Policy Text Block]	Intangible Assets The Company’s intangible assets are subject to impairment tests when events or circumstances indicate that an intangible asset (or asset group) may be impaired. The Company’s indefinite-lived intangible assets are also tested for impairment annually. There was no impairment of intangible assets during the year ended December 31, 2018 .
Other Current Liabilities [Policy Text Block]	Other Current Liabilities Other current liabilities include health savings account deposits ( $7.5 billion and $6.4 billion as of December 31, 2018 and 2017 , respectively), deposits under the Medicare Part D program, the RSF associated with the AARP Program, accruals for premium rebate payments under the ACA, the current portion of future policy benefits and customer balances.
Deferred Policy Acquisition Costs, Policy [Policy Text Block]	Policy Acquisition Costs The Company’s short duration health insurance contracts typically have a one-year term and may be canceled by the customer with at least 30 days’ notice. Costs related to the acquisition and renewal of short duration customer contracts are primarily charged to expense as incurred.
Consolidation, Subsidiaries or Other Investments, Consolidated Entities, Policy [Policy Text Block]	Redeemable Noncontrolling Interests Redeemable noncontrolling interests in the Company’s subsidiaries whose redemption is outside the control of the Company are classified as temporary equity. The following table provides details of the Company's redeemable noncontrolling interests’ activity for the years ended December 31, 2018 and 2017 : (in millions) 2018 2017 Redeemable noncontrolling interests, beginning of period $ 2,189 $ 2,012 Net earnings 123 71 Acquisitions 102 565 Redemptions (90 ) (309 ) Distributions (53 ) (38 ) Fair value and other adjustments (363 ) (112 ) Redeemable noncontrolling interests, end of period $ 1,908 $ 2,189
Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block]	Share-Based Compensation The Company recognizes compensation expense for share-based awards, including stock options, stock-settled stock appreciation rights (SARs) and restricted stock and restricted stock units (collectively, restricted shares), on a straight-line basis over the related service period (generally the vesting period) of the award, or to an employee’s eligible retirement date under the award agreement, if earlier. Restricted shares vest ratably, primarily over two to five years and compensation expense related to restricted shares is based on the share price on the date of grant. Stock options and SARs vest ratably primarily over four years and may be exercised up to 10 years from the date of grant. Compensation expense related to stock options and SARs is based on the fair value at the date of grant, which is estimated on the date of grant using a binomial option-pricing model. Under the Company’s Employee Stock Purchase Plan (ESPP), eligible employees are allowed to purchase the Company’s stock at a discounted price, which is 85% of the lower market price of the Company’s common stock at the beginning or at the end of the six-month purchase period. Share-based compensation expense for all programs is recognized in operating costs in the Consolidated Statements of Operations.
Earnings Per Share, Policy [Policy Text Block]	Net Earnings Per Common Share The Company computes basic earnings per common share attributable to UnitedHealth Group common shareholders by dividing net earnings attributable to UnitedHealth Group common shareholders by the weighted-average number of common shares outstanding during the period. The Company determines diluted net earnings per common share attributable to UnitedHealth Group common shareholders using the weighted-average number of common shares outstanding during the period, adjusted for potentially dilutive shares associated with stock options, SARs, restricted shares and the ESPP (collectively, common stock equivalents), using the treasury stock method. The treasury stock method assumes a hypothetical issuance of shares to settle the share-based awards, with the assumed proceeds used to purchase common stock at the average market price for the period. Assumed proceeds include the amount the employee must pay upon exercise and the average unrecognized compensation cost. The difference between the number of shares assumed issued and number of shares assumed purchased represents the dilutive shares.
Health Insurance Industry Tax, Policy [Policy Text Block]	Health Insurance Industry Tax The ACA includes an annual, nondeductible insurance industry tax (Health Insurance Industry Tax) to be levied proportionally across the insurance industry for risk-based health insurance products. A one year moratorium on the collection of the Health Insurance Industry Tax will occur in 2019. The Company estimates its liability for the Health Insurance Industry Tax based on a ratio of the Company’s applicable net premiums written compared to the U.S. health insurance industry total applicable net premiums, both for the previous calendar year. The Company records in full the estimated liability for the Health Insurance Industry Tax at the beginning of the calendar year with a corresponding deferred cost that is amortized to operating costs on the Consolidated Statements of Operations using a straight-line method over the calendar year. The liability is recorded in accounts payable and accrued liabilities and the corresponding deferred cost is recorded in prepaid expenses and other current assets on the Consolidated Balance Sheets.
New Accounting Pronouncements, Policy [Policy Text Block]	Recently Issued Accounting Standards In February 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standard Update (ASU) No. 2016-02, “Leases (Topic 842)” as modified by ASUs 2018-01, 2018-10, 2018-11 and 2018-20 (collectively, ASU 2016-02). Under ASU 2016-02, an entity is required to recognize assets and liabilities for the rights and obligations created by leases on the entity’s balance sheet for both finance and operating leases. For leases with a term of 12 months or less, the Company elected to not recognize lease assets and lease liabilities and expense the leases over a straight-line basis for the term of those leases. ASU 2016-02 requires new disclosures that depict the amount, timing and uncertainty of cash flows pertaining to an entity’s leases. The Company adopted ASU 2016-02 on January 1, 2019, using the cumulative effect upon adoption approach. The adoption resulted in no material impact to the Company’s balance sheet, results of operations, equity or cash flows. Recently Adopted Accounting Standards In January 2016, the FASB issued ASU 2016-01, “Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities” (ASU 2016-01). Most notably, the new guidance requires that equity investments, with certain exemptions, be measured at fair value with changes in fair value recognized in net income as opposed to other comprehensive income. The Company adopted ASU 2016-01 on a prospective basis effective January 1, 2018, as required, and reclassified $ 24 million from accumulated other comprehensive income to retained earnings. The Company has determined that there have been no other recently adopted or issued accounting standards that had, or will have, a material impact on its Consolidated Financial Statements.

Fair Value Fair Value (Policies

Fair Value Fair Value (Policies)	12 Months Ended
	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurement, Policy [Policy Text Block]	Certain assets and liabilities are measured at fair value in the Consolidated Financial Statements or have fair values disclosed in the Notes to the Consolidated Financial Statements. These assets and liabilities are classified into one of three levels of a hierarchy defined by GAAP. In instances in which the inputs used to measure fair value fall into different levels of the fair value hierarchy, the fair value measurement is categorized in its entirety based on the lowest level input that is significant to the fair value measurement in its entirety. The Company’s assessment of the significance of a particular item to the fair value measurement in its entirety requires judgment, including the consideration of inputs specific to the asset or liability. The fair value hierarchy is summarized as follows: Level 1 — Quoted prices (unadjusted) for identical assets/liabilities in active markets. Level 2 — Other observable inputs, either directly or indirectly, including: • Quoted prices for similar assets/liabilities in active markets; • Quoted prices for identical or similar assets/liabilities in inactive markets (e.g., few transactions, limited information, noncurrent prices, high variability over time); • Inputs other than quoted prices that are observable for the asset/liability (e.g., interest rates, yield curves, implied volatilities, credit spreads); and • Inputs that are corroborated by other observable market data. Level 3 — Unobservable inputs that cannot be corroborated by observable market data. There was no transfers in or out of Level 3 financial assets or liabilities during the year ended December 31, 2018 or 2017 . Nonfinancial assets and liabilities or financial assets and liabilities that are measured at fair value on a nonrecurring basis are subject to fair value adjustments only in certain circumstances, such as when the Company records an impairment. There were no significant fair value adjustments for these assets and liabilities recorded during the year ended December 31, 2018 or 2017 . The following methods and assumptions were used to estimate the fair value and determine the fair value hierarchy classification of each class of financial instrument included in the tables below: Cash and Cash Equivalents. The carrying value of cash and cash equivalents approximates fair value as maturities are less than three months. Fair values of cash equivalent instruments that do not trade on a regular basis in active markets are classified as Level 2. Debt and Equity Securities. Fair values of debt and equity securities are based on quoted market prices, where available. The Company obtains one price for each security primarily from a third-party pricing service (pricing service), which generally uses quoted or other observable inputs for the determination of fair value. The pricing service normally derives the security prices through recently reported trades for identical or similar securities, and, if necessary, makes adjustments through the reporting date based upon available observable market information. For securities not actively traded, the pricing service may use quoted market prices of comparable instruments or discounted cash flow analyses, incorporating inputs that are currently observable in the markets for similar securities. Inputs that are often used in the valuation methodologies include, but are not limited to, benchmark yields, credit spreads, default rates, prepayment speeds and nonbinding broker quotes. As the Company is responsible for the determination of fair value, it performs quarterly analyses on the prices received from the pricing service to determine whether the prices are reasonable estimates of fair value. Specifically, the Company compares the prices received from the pricing service to prices reported by a secondary pricing source, such as its custodian, its investment consultant and third-party investment advisors. Additionally, the Company compares changes in the reported market values and returns to relevant market indices to test the reasonableness of the reported prices. The Company’s internal price verification procedures and reviews of fair value methodology documentation provided by independent pricing services have not historically resulted in adjustment in the prices obtained from the pricing service. Fair values of debt securities that do not trade on a regular basis in active markets but are priced using other observable inputs are classified as Level 2. Fair value estimates for Level 1 and Level 2 equity securities are based on quoted market prices for actively traded equity securities and/or other market data for the same or comparable instruments and transactions in establishing the prices. The fair values of Level 3 investments in corporate bonds are estimated using valuation techniques that rely heavily on management assumptions and qualitative observations. Throughout the procedures discussed above in relation to the Company’s processes for validating third-party pricing information, the Company validates the understanding of assumptions and inputs used in security pricing and determines the proper classification in the hierarchy based on that understanding. Assets Under Management. Assets under management consists of debt securities and other investments held to fund costs associated with the AARP Program and are priced and classified using the same methodologies as the Company’s investments in debt and equity securities. Long-Term Debt. The fair values of the Company’s long-term debt are estimated and classified using the same methodologies as the Company’s investments in debt securities.

Schedule I (Policies)

Schedule I (Policies)	12 Months Ended
	Dec. 31, 2018
Condensed Financial Statements, Captions [Line Items]
Basis of Presentation and Significant Accounting Policies [Text Block]	Basis of Presentation, Use of Estimates and Significant Accounting Policies Basis of Presentation The Company has prepared the Consolidated Financial Statements according to U.S. Generally Accepted Accounting Principles (GAAP) and has included the accounts of UnitedHealth Group and its subsidiaries. Use of Estimates These Consolidated Financial Statements include certain amounts based on the Company’s best estimates and judgments. The Company’s most significant estimates relate to estimates and judgments for medical costs payable and revenues, valuation and impairment analysis of goodwill and other intangible assets and estimates of other current liabilities and other current receivables. Certain of these estimates require the application of complex assumptions and judgments, often because they involve matters that are inherently uncertain and will likely change in subsequent periods. The impact of any change in estimates is included in earnings in the period in which the estimate is adjusted. Revenues Premiums Premium revenues are primarily derived from risk-based health insurance arrangements in which the premium is typically at a fixed rate per individual served for a one-year period, and the Company assumes the economic risk of funding its customers’ health care and related administrative costs. Premium revenues are recognized in the period in which eligible individuals are entitled to receive health care benefits. Health care premium payments received from the Company’s customers in advance of the service period are recorded as unearned revenues. Fully insured commercial products of U.S. health plans, Medicare Advantage and Medicare Prescription Drug Benefit (Medicare Part D) plans with medical loss ratios as calculated under the definitions in the Patient Protection and Affordable Care Act (ACA) and related federal and state regulations and implementing regulation, that fall below certain targets are required to rebate ratable portions of their premiums annually. Medicare Advantage premium revenue includes the impact of the Centers for Medicare & Medicaid Services (CMS) quality bonuses based on plans’ Star ratings. Premium revenues are recognized based on the estimated premiums earned, net of projected rebates, because the Company is able to reasonably estimate the ultimate premiums of these contracts. The Company also records premium revenues from capitation arrangements at its OptumHealth businesses. The Company’s Medicare Advantage and Medicare Part D premium revenues are subject to periodic adjustment under CMS’ risk adjustment payment methodology. CMS deploys a risk adjustment model that apportions premiums paid to all health plans according to health severity and certain demographic factors. The CMS risk adjustment model provides higher per member payments for enrollees diagnosed with certain conditions and lower payments for enrollees who are healthier. Under this risk adjustment methodology, CMS calculates the risk adjusted premium payment using diagnosis data from hospital inpatient, hospital outpatient and physician treatment settings. The Company and health care providers collect, capture and submit the necessary and available diagnosis data to CMS within prescribed deadlines. The Company estimates risk adjustment premium revenues based upon the diagnosis data submitted and expected to be submitted to CMS. Risk adjustment data for the Company’s plans are subject to review by the government, including audit by regulators. See Note 12 for additional information regarding these audits. Products and Services For the Company’s OptumRx pharmacy care services business, the majority of revenues are derived from products sold through a contracted network of retail pharmacies or home delivery, specialty and compounding pharmacy facilities. Product revenues include ingredient costs (net of rebates), a negotiated dispensing fee and customer co-payments for drugs dispensed through the Company’s mail-service pharmacy. In retail pharmacy transactions, revenues recognized exclude the member’s applicable co-payment. Pharmacy products are billed to customers based on the number of transactions occurring during the billing period. Product revenues are recognized when the prescriptions are dispensed through the retail network or received by consumers through the Company’s mail-service pharmacy. The Company has entered into contracts in which it is primarily obligated to pay its network pharmacy providers for benefits provided to their customers regardless of whether the Company is paid. The Company is also involved in establishing the prices charged by retail pharmacies, determining which drugs will be included in formulary listings and selecting which retail pharmacies will be included in the network offered to plan sponsors’ members and accordingly, are reported on a gross basis. Services revenue consists of fees derived from services performed for customers that self-insure the health care costs of their employees and employees’ dependents. Under service fee contracts, the Company receives monthly, a fixed fee per employee, which is recognized as revenue as the Company performs, or makes available, the applicable services to the customer. The customers retain the risk of financing health care costs for their employees and employees’ dependents, and the Company administers the payment of customer funds to physicians and other health care professionals from customer-funded bank accounts. As the Company has neither the obligation for funding the health care costs, nor the primary responsibility for providing the medical care, the Company does not recognize premium revenue and medical costs for these contracts in its Consolidated Financial Statements. For these fee-based customer arrangements, the Company provides coordination and facilitation of medical services; transaction processing; customer, consumer and care professional services; and access to contracted networks of physicians, hospitals and other health care professionals. These services are performed throughout the contract period. Revenues are also comprised of a number of services and products sold through Optum. OptumHealth’s service revenues include net patient service revenues that are recorded based upon established billing rates, less allowances for contractual adjustments, and are recognized as services are provided. For its financial services offerings, OptumHealth charges fees and earns investment income on managed funds. OptumInsight provides software and information products, advisory consulting arrangements and services outsourcing contracts, which may be delivered over several years. OptumInsight revenues are generally recognized over time and measured each period based on the progress to date as services are performed or made available to customers. As of December 31, 2018 and 2017 , accounts receivables related to products and services were $3.9 billion and $3.7 billion , respectively. In 2018 and 2017 , the Company had no material bad-debt expense and there were no material contract assets, contract liabilities or deferred contract costs recorded on the Consolidated Balance Sheets as of December 31, 2018 or 2017 . For the years ended December 31, 2018 and 2017 , revenue recognized from performance obligations related to prior periods (for example, due to changes in transaction price) was not material. Revenue expected to be recognized in any future year related to remaining performance obligations, excluding revenue pertaining to contracts that have an original expected duration of one year or less, contracts where revenue is recognized as invoiced and contracts with variable consideration related to undelivered performance obligations, is not material. See Note 13 for disaggregation of revenue by segment and type. Medical Costs and Medical Costs Payable The Company’s estimate of medical costs payable represents management’s best estimate of its liability for unpaid medical costs as of December 31, 2018. Each period, the Company re-examines previously established medical costs payable estimates based on actual claim submissions and other changes in facts and circumstances. As more complete claim information becomes available, the Company adjusts the amount of the estimates and includes the changes in estimates in medical costs in the period in which the change is identified. Approximately 90% of claims related to medical care services are known and settled within 90 days from the date of service and substantially all within twelve months. Medical costs and medical costs payable include estimates of the Company’s obligations for medical care services that have been rendered on behalf of insured consumers, but for which claims have either not yet been received, processed, or paid. The Company develops estimates for medical care services incurred but not reported (IBNR), which includes estimates for claims that have not been received or fully processed, using an actuarial process that is consistently applied, centrally controlled and automated. The actuarial models consider factors such as time from date of service to claim processing, seasonal variances in medical care consumption, health care professional contract rate changes, medical care utilization and other medical cost trends, membership volume and demographics, the introduction of new technologies, benefit plan changes, and business mix changes related to products, customers and geography. In developing its medical costs payable estimates, the Company applies different estimation methods depending on which incurred claims are being estimated. For the most recent two months, the Company estimates claim costs incurred by applying observed medical cost trend factors to the average per member per month (PMPM) medical costs incurred in prior months for which more complete claim data are available, supplemented by a review of near-term completion factors (actuarial estimates, based upon historical experience and analysis of current trends, of the percentage of incurred claims during a given period that have been adjudicated by the Company at the date of estimation). For months prior to the most recent two months, the Company applies the completion factors to actual claims adjudicated-to-date to estimate the expected amount of ultimate incurred claims for those months. Cost of Products Sold The Company’s cost of products sold includes the cost of pharmaceuticals dispensed to unaffiliated customers either directly at its home delivery and specialty pharmacy locations, or indirectly through its nationwide network of participating pharmacies. Rebates attributable to non-affiliated clients are accrued as rebates receivable and a reduction of cost of products sold, with a corresponding payable for the amounts of the rebates to be remitted to those non-affiliated clients in accordance with their contracts and recorded in the Consolidated Statements of Operations as a reduction of product revenue. Cost of products sold also includes the cost of personnel to support the Company’s transaction processing services, system sales, maintenance and professional services. Cash, Cash Equivalents and Investments Cash and cash equivalents are highly liquid investments that have an original maturity of three months or less. The fair value of cash and cash equivalents approximates their carrying value because of the short maturity of the instruments. Investments with maturities of less than one year are classified as short-term. Because of regulatory requirements, certain investments are included in long-term investments regardless of their maturity date. The Company classifies these investments as held-to-maturity and reports them at amortized cost. Substantially all other investments are classified as available-for-sale and reported at fair value based on quoted market prices, where available. Equity investments, with certain exceptions, are measured at fair value with changes in fair value recognized in net earnings. The Company excludes unrealized gains and losses on investments in available-for-sale debt securities from net earnings and reports them as comprehensive income and, net of income tax effects, as a separate component of equity. To calculate realized gains and losses on the sale of debt securities, the Company specifically identifies the cost of each investment sold. The Company evaluates an investment for impairment by considering the length of time and extent to which market value has been less than cost or amortized cost, the financial condition and near-term prospects of the issuer as well as specific events or circumstances that may influence the operations of the issuer and the Company’s intent to sell the security or the likelihood that it will be required to sell the security before recovery of the entire amortized cost. New information and the passage of time can change these judgments. The Company manages its investment portfolio to limit its exposure to any one issuer or market sector, and largely limits its investments to investment grade quality. Securities downgraded below policy minimums after purchase will be disposed of in accordance with the Company’s investment policy. Assets Under Management The Company provides health insurance products and services to members of AARP under a Supplemental Health Insurance Program (the AARP Program) and to AARP members and non-members under separate Medicare Advantage and Medicare Part D arrangements. The products and services under the AARP Program include supplemental Medicare benefits, hospital indemnity insurance, including insurance for individuals between 50 to 64 years of age, and other related products. Pursuant to the Company’s agreement, AARP Program assets are managed separately from the Company’s general investment portfolio and are used to pay costs associated with the AARP Program. These assets are invested at the Company’s discretion, within investment guidelines approved by AARP. The Company does not guarantee any rates of return on these investments and, upon any transfer of the AARP Program contract to another entity, the Company would transfer cash equal in amount to the fair value of these investments at the date of transfer to that entity. Because the purpose of these assets is to fund the medical costs payable, the rate stabilization fund (RSF) liabilities and other related liabilities associated with this AARP contract, assets under management are classified as current assets, consistent with the classification of these liabilities. The effects of changes in other balance sheet amounts associated with the AARP Program also accrue to the overall benefit of the AARP policyholders through the RSF balance. Accordingly, the Company excludes the effect of such changes in its Consolidated Statements of Cash Flows. Other Current Receivables Other current receivables include amounts due from pharmaceutical manufacturers for rebates and other miscellaneous amounts due to the Company. The Company’s pharmacy care services businesses contract with pharmaceutical manufacturers, some of which provide rebates based on use of the manufacturers’ products by its affiliated and non-affiliated clients. The Company accrues rebates as they are earned by its clients on a monthly basis based on the terms of the applicable contracts, historical data and current estimates. The pharmacy care services businesses bill these rebates to the manufacturers on a monthly or quarterly basis depending on the contractual terms and record rebates attributable to affiliated clients as a reduction to medical costs. The Company generally receives rebates two to five months after billing. As of December 31, 2018 and 2017, total pharmaceutical manufacturer rebates receivable included in other receivables in the Consolidated Balance Sheets amounted to $4.2 billion and $3.8 billion , respectively. Property, Equipment and Capitalized Software Property, equipment and capitalized software are stated at cost, net of accumulated depreciation and amortization. Capitalized software consists of certain costs incurred in the development of internal-use software, including external direct costs of materials and services and applicable payroll costs of employees devoted to specific software development. The Company calculates depreciation and amortization using the straight-line method over the estimated useful lives of the assets. The useful lives for property, equipment and capitalized software are: Furniture, fixtures and equipment 3 to 10 years Buildings 35 to 40 years Capitalized software 3 to 5 years Leasehold improvements are depreciated over the shorter of the remaining lease term or their estimated useful economic life. Goodwill To determine whether goodwill is impaired, annually or more frequently if needed, the Company performs a multi-step impairment test. The Company may first assess qualitative factors to determine if it is more likely than not that the carrying value of a reporting unit exceeds its estimated fair value. The Company may also elect to skip the qualitative testing and proceed directly to the quantitative testing. When performing quantitative testing, the Company first estimates the fair values of its reporting units using discounted cash flows. To determine fair values, the Company must make assumptions about a wide variety of internal and external factors. Significant assumptions used in the impairment analysis include financial projections of free cash flow (including significant assumptions about operations, capital requirements and income taxes), long-term growth rates for determining terminal value and discount rates. Comparative market multiples are used to corroborate the results of the discounted cash flow test. If the fair value is less than the carrying value of the reporting unit, then the implied value of goodwill would be calculated and compared to the carrying amount of goodwill to determine whether goodwill is impaired. There was no impairment of goodwill during the year ended December 31, 2018 . Intangible Assets The Company’s intangible assets are subject to impairment tests when events or circumstances indicate that an intangible asset (or asset group) may be impaired. The Company’s indefinite-lived intangible assets are also tested for impairment annually. There was no impairment of intangible assets during the year ended December 31, 2018 . Other Current Liabilities Other current liabilities include health savings account deposits ( $7.5 billion and $6.4 billion as of December 31, 2018 and 2017 , respectively), deposits under the Medicare Part D program, the RSF associated with the AARP Program, accruals for premium rebate payments under the ACA, the current portion of future policy benefits and customer balances. Policy Acquisition Costs The Company’s short duration health insurance contracts typically have a one-year term and may be canceled by the customer with at least 30 days’ notice. Costs related to the acquisition and renewal of short duration customer contracts are primarily charged to expense as incurred. Redeemable Noncontrolling Interests Redeemable noncontrolling interests in the Company’s subsidiaries whose redemption is outside the control of the Company are classified as temporary equity. The following table provides details of the Company's redeemable noncontrolling interests’ activity for the years ended December 31, 2018 and 2017 : (in millions) 2018 2017 Redeemable noncontrolling interests, beginning of period $ 2,189 $ 2,012 Net earnings 123 71 Acquisitions 102 565 Redemptions (90 ) (309 ) Distributions (53 ) (38 ) Fair value and other adjustments (363 ) (112 ) Redeemable noncontrolling interests, end of period $ 1,908 $ 2,189 Share-Based Compensation The Company recognizes compensation expense for share-based awards, including stock options, stock-settled stock appreciation rights (SARs) and restricted stock and restricted stock units (collectively, restricted shares), on a straight-line basis over the related service period (generally the vesting period) of the award, or to an employee’s eligible retirement date under the award agreement, if earlier. Restricted shares vest ratably, primarily over two to five years and compensation expense related to restricted shares is based on the share price on the date of grant. Stock options and SARs vest ratably primarily over four years and may be exercised up to 10 years from the date of grant. Compensation expense related to stock options and SARs is based on the fair value at the date of grant, which is estimated on the date of grant using a binomial option-pricing model. Under the Company’s Employee Stock Purchase Plan (ESPP), eligible employees are allowed to purchase the Company’s stock at a discounted price, which is 85% of the lower market price of the Company’s common stock at the beginning or at the end of the six-month purchase period. Share-based compensation expense for all programs is recognized in operating costs in the Consolidated Statements of Operations. Net Earnings Per Common Share The Company computes basic earnings per common share attributable to UnitedHealth Group common shareholders by dividing net earnings attributable to UnitedHealth Group common shareholders by the weighted-average number of common shares outstanding during the period. The Company determines diluted net earnings per common share attributable to UnitedHealth Group common shareholders using the weighted-average number of common shares outstanding during the period, adjusted for potentially dilutive shares associated with stock options, SARs, restricted shares and the ESPP (collectively, common stock equivalents), using the treasury stock method. The treasury stock method assumes a hypothetical issuance of shares to settle the share-based awards, with the assumed proceeds used to purchase common stock at the average market price for the period. Assumed proceeds include the amount the employee must pay upon exercise and the average unrecognized compensation cost. The difference between the number of shares assumed issued and number of shares assumed purchased represents the dilutive shares. Health Insurance Industry Tax The ACA includes an annual, nondeductible insurance industry tax (Health Insurance Industry Tax) to be levied proportionally across the insurance industry for risk-based health insurance products. A one year moratorium on the collection of the Health Insurance Industry Tax will occur in 2019. The Company estimates its liability for the Health Insurance Industry Tax based on a ratio of the Company’s applicable net premiums written compared to the U.S. health insurance industry total applicable net premiums, both for the previous calendar year. The Company records in full the estimated liability for the Health Insurance Industry Tax at the beginning of the calendar year with a corresponding deferred cost that is amortized to operating costs on the Consolidated Statements of Operations using a straight-line method over the calendar year. The liability is recorded in accounts payable and accrued liabilities and the corresponding deferred cost is recorded in prepaid expenses and other current assets on the Consolidated Balance Sheets. Recently Issued Accounting Standards In February 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standard Update (ASU) No. 2016-02, “Leases (Topic 842)” as modified by ASUs 2018-01, 2018-10, 2018-11 and 2018-20 (collectively, ASU 2016-02). Under ASU 2016-02, an entity is required to recognize assets and liabilities for the rights and obligations created by leases on the entity’s balance sheet for both finance and operating leases. For leases with a term of 12 months or less, the Company elected to not recognize lease assets and lease liabilities and expense the leases over a straight-line basis for the term of those leases. ASU 2016-02 requires new disclosures that depict the amount, timing and uncertainty of cash flows pertaining to an entity’s leases. The Company adopted ASU 2016-02 on January 1, 2019, using the cumulative effect upon adoption approach. The adoption resulted in no material impact to the Company’s balance sheet, results of operations, equity or cash flows. Recently Adopted Accounting Standards In January 2016, the FASB issued ASU 2016-01, “Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities” (ASU 2016-01). Most notably, the new guidance requires that equity investments, with certain exemptions, be measured at fair value with changes in fair value recognized in net income as opposed to other comprehensive income. The Company adopted ASU 2016-01 on a prospective basis effective January 1, 2018, as required, and reclassified $ 24 million from accumulated other comprehensive income to retained earnings. The Company has determined that there have been no other recently adopted or issued accounting standards that had, or will have, a material impact on its Consolidated Financial Statements.
Consolidation, Subsidiaries or Other Investments, Consolidated Entities, Policy [Policy Text Block]	Redeemable Noncontrolling Interests Redeemable noncontrolling interests in the Company’s subsidiaries whose redemption is outside the control of the Company are classified as temporary equity. The following table provides details of the Company's redeemable noncontrolling interests’ activity for the years ended December 31, 2018 and 2017 : (in millions) 2018 2017 Redeemable noncontrolling interests, beginning of period $ 2,189 $ 2,012 Net earnings 123 71 Acquisitions 102 565 Redemptions (90 ) (309 ) Distributions (53 ) (38 ) Fair value and other adjustments (363 ) (112 ) Redeemable noncontrolling interests, end of period $ 1,908 $ 2,189
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Basis of Presentation and Significant Accounting Policies [Text Block]	Basis of Presentation UnitedHealth Group’s parent company financial information has been derived from its consolidated financial statements and should be read in conjunction with the consolidated financial statements included in this Form 10-K. The accounting policies for the registrant are the same as those described in Note 2 of Notes to the Consolidated Financial Statements included in Part II, Item 8, “Financial Statements and Supplementary Data.”
Consolidation, Subsidiaries or Other Investments, Consolidated Entities, Policy [Policy Text Block]	Subsidiary Transactions Investment in Subsidiaries. UnitedHealth Group’s investment in subsidiaries is stated at cost plus equity in undistributed earnings of subsidiaries.

Basis of Presentation, Uses o_3

Basis of Presentation, Uses of Estimates and Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2018
Property, Plant and Equipment [Table Text Block]	A summary of property, equipment and capitalized software is as follows: (in millions) December 31, 2018 December 31, 2017 Land and improvements $ 566 $ 405 Buildings and improvements 4,470 3,664 Computer equipment 1,984 1,829 Furniture and fixtures 1,525 1,208 Less accumulated depreciation (2,787 ) (2,488 ) Property and equipment, net 5,758 4,618 Capitalized software 4,054 3,601 Less accumulated amortization (1,354 ) (1,206 ) Capitalized software, net 2,700 2,395 Total property, equipment and capitalized software, net $ 8,458 $ 7,013
Redeemable Noncontrolling Interest [Table Text Block]	The following table provides details of the Company's redeemable noncontrolling interests’ activity for the years ended December 31, 2018 and 2017 : (in millions) 2018 2017 Redeemable noncontrolling interests, beginning of period $ 2,189 $ 2,012 Net earnings 123 71 Acquisitions 102 565 Redemptions (90 ) (309 ) Distributions (53 ) (38 ) Fair value and other adjustments (363 ) (112 ) Redeemable noncontrolling interests, end of period $ 1,908 $ 2,189
Useful Life [Member]
Property, Plant and Equipment [Table Text Block]	The Company calculates depreciation and amortization using the straight-line method over the estimated useful lives of the assets. The useful lives for property, equipment and capitalized software are: Furniture, fixtures and equipment 3 to 10 years Buildings 35 to 40 years Capitalized software 3 to 5 years

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2018
Short-Term and Long-Term Investments [Table Text Block]	A summary of debt securities by major security type is as follows: (in millions) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value December 31, 2018 Debt securities - available-for-sale: U.S. government and agency obligations $ 3,434 $ 13 $ (42 ) $ 3,405 State and municipal obligations 7,117 61 (57 ) 7,121 Corporate obligations 15,366 14 (218 ) 15,162 U.S. agency mortgage-backed securities 4,947 11 (106 ) 4,852 Non-U.S. agency mortgage-backed securities 1,376 2 (20 ) 1,358 Total debt securities - available-for-sale 32,240 101 (443 ) 31,898 Debt securities - held-to-maturity: U.S. government and agency obligations 255 1 (2 ) 254 State and municipal obligations 11 — — 11 Corporate obligations 355 — — 355 Total debt securities - held-to-maturity 621 1 (2 ) 620 Total debt securities $ 32,861 $ 102 $ (445 ) $ 32,518 December 31, 2017 Debt securities - available-for-sale: U.S. government and agency obligations $ 2,673 $ 1 $ (30 ) $ 2,644 State and municipal obligations 7,596 99 (35 ) 7,660 Corporate obligations 13,181 57 (44 ) 13,194 U.S. agency mortgage-backed securities 3,942 7 (38 ) 3,911 Non-U.S. agency mortgage-backed securities 1,018 3 (6 ) 1,015 Total debt securities - available-for-sale 28,410 167 (153 ) 28,424 Debt securities - held-to-maturity: U.S. government and agency obligations 254 1 (1 ) 254 State and municipal obligations 2 — — 2 Corporate obligations 280 — — 280 Total debt securities - held-to-maturity 536 1 (1 ) 536 Total debt securities $ 28,946 $ 168 $ (154 ) $ 28,960
Investments by Contractual Maturity [Table Text Block]	The amortized cost and fair value of debt securities as of December 31, 2018 , by contractual maturity, were as follows: Available-for-Sale Held-to-Maturity (in millions) Amortized Cost Fair Value Amortized Fair Due in one year or less $ 3,560 $ 3,551 $ 150 $ 150 Due after one year through five years 12,432 12,297 213 212 Due after five years through ten years 7,362 7,270 129 129 Due after ten years 2,563 2,570 129 129 U.S. agency mortgage-backed securities 4,947 4,852 — — Non-U.S. agency mortgage-backed securities 1,376 1,358 — — Total debt securities $ 32,240 $ 31,898 $ 621 $ 620
Fair Value of Available-for-Sale Investments with Gross Unrealized Losses by Investment Type and Length of Time that Individual Securities have been in a Continuous Unrealized Loss Position [Table Text Block]	The fair value of available-for-sale investments with gross unrealized losses by major security type and length of time that individual securities have been in a continuous unrealized loss position were as follows: Less Than 12 Months 12 Months or Greater Total (in millions) Fair Value Gross Unrealized Losses Fair Value Gross Fair Value Gross December 31, 2018 Debt securities - available-for-sale: U.S. government and agency obligations $ 998 $ (7 ) $ 1,425 $ (35 ) $ 2,423 $ (42 ) State and municipal obligations 1,334 (11 ) 2,491 (46 ) 3,825 (57 ) Corporate obligations 8,105 (109 ) 4,239 (109 ) 12,344 (218 ) U.S. agency mortgage-backed securities 1,296 (22 ) 2,388 (84 ) 3,684 (106 ) Non-U.S. agency mortgage-backed securities 622 (7 ) 459 (13 ) 1,081 (20 ) Total debt securities - available-for-sale $ 12,355 $ (156 ) $ 11,002 $ (287 ) $ 23,357 $ (443 ) December 31, 2017 Debt securities - available-for-sale: U.S. government and agency obligations $ 1,249 $ (8 ) $ 1,027 $ (22 ) $ 2,276 $ (30 ) State and municipal obligations 2,599 (21 ) 866 (14 ) 3,465 (35 ) Corporate obligations 5,901 (23 ) 1,242 (21 ) 7,143 (44 ) U.S. agency mortgage-backed securities 1,657 (12 ) 1,162 (26 ) 2,819 (38 ) Non-U.S. agency mortgage-backed securities 411 (3 ) 144 (3 ) 555 (6 ) Total debt securities - available-for-sale $ 11,817 $ (67 ) $ 4,441 $ (86 ) $ 16,258 $ (153 )

Fair Value (Tables)

Fair Value (Tables)	12 Months Ended
	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets and Liabilities, Measured at Fair Value Recurring Basis [Table Text Block]	The following table presents a summary of fair value measurements by level and carrying values for items measured at fair value on a recurring basis in the Consolidated Balance Sheets: (in millions) Quoted Prices in Active Markets (Level 1) Other Observable Inputs (Level 2) Unobservable Inputs (Level 3) Total Fair and Carrying Value December 31, 2018 Cash and cash equivalents $ 10,757 $ 109 $ — $ 10,866 Debt securities - available-for-sale: U.S. government and agency obligations 3,060 345 — 3,405 State and municipal obligations — 7,121 — 7,121 Corporate obligations 39 14,950 173 15,162 U.S. agency mortgage-backed securities — 4,852 — 4,852 Non-U.S. agency mortgage-backed securities — 1,358 — 1,358 Total debt securities - available-for-sale 3,099 28,626 173 31,898 Equity securities 1,832 13 — 1,845 Assets under management 1,086 1,938 8 3,032 Total assets at fair value $ 16,774 $ 30,686 $ 181 $ 47,641 Percentage of total assets at fair value 35 % 65 % — % 100 % December 31, 2017 Cash and cash equivalents $ 11,718 $ 263 $ — $ 11,981 Debt securities - available-for-sale: U.S. government and agency obligations 2,428 216 — 2,644 State and municipal obligations — 7,660 — 7,660 Corporate obligations 65 12,989 140 13,194 U.S. agency mortgage-backed securities — 3,911 — 3,911 Non-U.S. agency mortgage-backed securities — 1,015 — 1,015 Total debt securities - available-for-sale 2,493 25,791 140 28,424 Equity securities 1,784 14 194 1,992 Assets under management 1,117 1,984 — 3,101 Total assets at fair value $ 17,112 $ 28,052 $ 334 $ 45,498 Percentage of total assets at fair value 38 % 61 % 1 % 100 %
Fair Value Measurements, Nonrecurring [Table Text Block]	The following table presents a summary of fair value measurements by level and carrying values for certain financial instruments not measured at fair value on a recurring basis in the Consolidated Balance Sheets: (in millions) Quoted Prices in Active Markets (Level 1) Other Observable Inputs (Level 2) Unobservable Inputs (Level 3) Total Fair Value Total Carrying Value December 31, 2018 Debt securities - held-to-maturity $ 260 $ 65 $ 295 $ 620 $ 621 Long-term debt and other financing obligations $ — $ 37,944 $ — $ 37,944 $ 36,554 December 31, 2017 Debt securities - held-to-maturity $ 267 $ 4 $ 265 $ 536 $ 536 Long-term debt and other financing obligations $ — $ 34,504 $ — $ 34,504 $ 31,542

Property, Plant, and Capitali_2

Property, Plant, and Capitalized Software (Tables)	12 Months Ended
	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment [Table Text Block]	A summary of property, equipment and capitalized software is as follows: (in millions) December 31, 2018 December 31, 2017 Land and improvements $ 566 $ 405 Buildings and improvements 4,470 3,664 Computer equipment 1,984 1,829 Furniture and fixtures 1,525 1,208 Less accumulated depreciation (2,787 ) (2,488 ) Property and equipment, net 5,758 4,618 Capitalized software 4,054 3,601 Less accumulated amortization (1,354 ) (1,206 ) Capitalized software, net 2,700 2,395 Total property, equipment and capitalized software, net $ 8,458 $ 7,013

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2018
Goodwill [Line Items]
Schedule of Goodwill [Table Text Block]	Changes in the carrying amount of goodwill, by reportable segment, were as follows: (in millions) UnitedHealthcare OptumHealth OptumInsight OptumRx Consolidated Balance at January 1, 2017 $ 23,854 $ 6,322 $ 4,449 $ 12,959 $ 47,584 Acquisitions 690 5,189 1,221 — 7,100 Foreign currency effects and adjustments, net (60 ) (23 ) 4 (49 ) (128 ) Balance at December 31, 2017 24,484 11,488 5,674 12,910 54,556 Acquisitions 2,723 471 106 1,881 5,181 Foreign currency effects and adjustments, net (807 ) (12 ) (8 ) — (827 ) Balance at December 31, 2018 $ 26,400 $ 11,947 $ 5,772 $ 14,791 $ 58,910
Schedule of Acquired Finite-Lived Intangible Assets by Major Class [Table Text Block]	The gross carrying value, accumulated amortization and net carrying value of other intangible assets were as follows: December 31, 2018 December 31, 2017 (in millions) Gross Carrying Value Accumulated Amortization Net Carrying Value Gross Carrying Value Accumulated Amortization Net Carrying Value Customer-related $ 11,622 $ (3,908 ) $ 7,714 $ 10,832 $ (3,743 ) $ 7,089 Trademarks and technology 1,122 (512 ) 610 1,054 (432 ) 622 Trademarks and other indefinite-lived 745 — 745 561 — 561 Other 428 (172 ) 256 351 (134 ) 217 Total $ 13,917 $ (4,592 ) $ 9,325 $ 12,798 $ (4,309 ) $ 8,489
Schedule of Finite-Lived Intangible Assets Acquired as Part of Business Combination [Table Text Block]	The acquisition date fair values and weighted-average useful lives assigned to finite-lived intangible assets acquired in business combinations consisted of the following by year of acquisition: 2018 2017 (in millions, except years) Fair Value Weighted-Average Useful Life Fair Value Weighted-Average Useful Life Customer-related $ 1,355 17 years $ 324 13 years Trademarks and technology 122 4 years 367 11 years Other 97 9 years 82 6 years Total acquired finite-lived intangible assets $ 1,574 16 years $ 773 11 years
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block]	Estimated full year amortization expense relating to intangible assets for each of the next five years ending December 31 is as follows: (in millions) 2019 $ 889 2020 795 2021 724 2022 632 2023 593

Medical Costs Payable (Tables)

Medical Costs Payable (Tables)	12 Months Ended
	Dec. 31, 2018
Insurance [Abstract]
Schedule of Liability for Unpaid Claims and Claims Adjustment Expense [Table Text Block]	The following table shows the components of the change in medical costs payable for the years ended December 31: (in millions) 2018 2017 2016 Medical costs payable, beginning of period $ 17,871 $ 16,391 $ 14,330 Acquisitions 339 83 — Reported medical costs: Current year 145,723 130,726 117,258 Prior years (320 ) (690 ) (220 ) Total reported medical costs 145,403 130,036 117,038 Medical payments: Payments for current year (127,155 ) (113,811 ) (101,696 ) Payments for prior years (16,567 ) (14,828 ) (13,281 ) Total medical payments (143,722 ) (128,639 ) (114,977 ) Medical costs payable, end of period $ 19,891 $ 17,871 $ 16,391
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Table Text Block]	The following is information about incurred and paid medical cost development as of December 31, 2018 : Net Incurred Medical Costs (in millions) For the Years ended December 31, Year 2017 2018 2017 $ 130,726 $ 130,441 2018 145,723 Total $ 276,164 Net Cumulative Medical Payments (in millions) For the Years ended December 31, Year 2017 2018 2017 $ (113,811 ) $ (129,778 ) 2018 (127,155 ) Total (256,933 ) Net remaining outstanding liabilities prior to 2017 660 Total medical costs payable $ 19,891

Commercial Paper and Long-Ter_2

Commercial Paper and Long-Term Debt (Tables)	12 Months Ended
	Dec. 31, 2018
Debt Instrument [Line Items]
Commercial Paper and Long-Term Debt [Table Text Block]	Commercial paper and senior unsecured long-term debt consisted of the following: December 31, 2018 December 31, 2017 (in millions, except percentages) Par Value Carrying Value Fair Value Par Value Carrying Value Fair Value Commercial paper $ — $ — $ — $ 150 $ 150 $ 150 6.000% notes due February 2018 — — — 1,100 1,101 1,106 1.900% notes due July 2018 — — — 1,500 1,499 1,501 1.700% notes due February 2019 750 750 749 750 749 747 1.625% notes due March 2019 500 500 499 500 501 497 2.300% notes due December 2019 500 494 497 500 495 501 2.700% notes due July 2020 1,500 1,498 1,494 1,500 1,496 1,517 Floating rate notes due October 2020 300 299 298 300 299 300 3.875% notes due October 2020 450 443 456 450 446 467 1.950% notes due October 2020 900 897 884 900 895 892 4.700% notes due February 2021 400 398 412 400 403 425 2.125% notes due March 2021 750 747 734 750 746 744 Floating rate notes due June 2021 350 349 347 — — — 3.150% notes due June 2021 400 399 400 — — — 3.375% notes due November 2021 500 489 503 500 493 516 2.875% notes due December 2021 750 735 748 750 741 760 2.875% notes due March 2022 1,100 1,051 1,091 1,100 1,054 1,114 3.350% notes due July 2022 1,000 997 1,005 1,000 996 1,033 2.375% notes due October 2022 900 894 872 900 893 891 0.000% notes due November 2022 15 12 13 15 12 12 2.750% notes due February 2023 625 602 611 625 606 626 2.875% notes due March 2023 750 750 739 750 762 759 3.500% notes due June 2023 750 746 756 — — — 3.500% notes due February 2024 750 745 755 — — — 3.750% notes due July 2025 2,000 1,989 2,025 2,000 1,987 2,108 3.700% notes due December 2025 300 298 303 — — — 3.100% notes due March 2026 1,000 995 965 1,000 995 1,007 3.450% notes due January 2027 750 746 742 750 745 776 3.375% notes due April 2027 625 619 611 625 618 642 2.950% notes due October 2027 950 938 898 950 937 947 3.850% notes due June 2028 1,150 1,142 1,163 — — — 3.875% notes due December 2028 850 842 861 — — — 4.625% notes due July 2035 1,000 992 1,060 1,000 991 1,165 5.800% notes due March 2036 850 838 1,003 850 837 1,105 6.500% notes due June 2037 500 492 638 500 491 698 6.625% notes due November 2037 650 641 841 650 641 923 6.875% notes due February 2038 1,100 1,076 1,437 1,100 1,075 1,596 5.700% notes due October 2040 300 296 355 300 296 389 5.950% notes due February 2041 350 345 426 350 345 466 4.625% notes due November 2041 600 588 627 600 588 685 4.375% notes due March 2042 502 484 503 502 483 555 3.950% notes due October 2042 625 607 596 625 607 650 4.250% notes due March 2043 750 734 744 750 734 822 4.750% notes due July 2045 2,000 1,973 2,116 2,000 1,972 2,362 4.200% notes due January 2047 750 738 745 750 738 808 4.250% notes due April 2047 725 717 719 725 717 798 3.750% notes due October 2047 950 933 869 950 933 969 4.250% notes due June 2048 1,350 1,329 1,349 — — — 4.450% notes due December 2048 1,100 1,087 1,132 — — — Total commercial paper and long-term debt $ 35,667 $ 35,234 $ 36,591 $ 31,417 $ 31,067 $ 34,029
Schedule of Maturities of Long-term Debt [Table Text Block]	Maturities of long-term debt for the years ending December 31 are as follows: (in millions) 2019 $ 1,973 2020 3,350 2021 3,350 2022 3,215 2023 2,325 Thereafter 22,775

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2018
Income Tax Contingency [Line Items]
Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]	The components of the provision for income taxes for the years ended December 31 are as follows: (in millions) 2018 2017 2016 Current Provision: Federal $ 2,897 $ 3,597 $ 4,302 State and local 219 314 312 Foreign 404 254 95 Total current provision 3,520 4,165 4,709 Deferred provision (benefit) 42 (965 ) 81 Total provision for income taxes $ 3,562 $ 3,200 $ 4,790
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]	The reconciliation of the tax provision at the U.S. federal statutory rate to the provision for income taxes and the effective tax rate for the years ended December 31 is as follows: (in millions, except percentages) 2018 2017 2016 Tax provision at the U.S. federal statutory rate $ 3,348 21.0 % $ 4,908 35.0 % $ 4,152 35.0 % Change in tax law — — (1,199 ) (8.6 ) — — State income taxes, net of federal benefit 168 1.0 197 1.4 205 1.7 Share-based awards - excess tax benefit (161 ) (1.0 ) (319 ) (2.3 ) (158 ) (1.3 ) Non-deductible compensation 117 0.7 175 1.3 128 1.1 Health insurance industry tax 552 3.5 — — 645 5.4 Foreign rate differential (203 ) (1.3 ) (282 ) (2.0 ) (105 ) (0.9 ) Other, net (259 ) (1.6 ) (280 ) (2.0 ) (77 ) (0.6 ) Provision for income taxes $ 3,562 22.3 % $ 3,200 22.8 % $ 4,790 40.4 %
Schedule of Deferred Tax Assets and Liabilities [Table Text Block]	The components of deferred income tax assets and liabilities as of December 31 are as follows: (in millions) 2018 2017 Deferred income tax assets: Accrued expenses and allowances $ 551 $ 544 U.S. federal and state net operating loss carryforwards 190 216 Share-based compensation 91 97 Nondeductible liabilities 184 169 Non-U.S. tax loss carryforwards 426 445 Other-domestic 306 167 Other-non-U.S. 337 198 Subtotal 2,085 1,836 Less: valuation allowances (84 ) (64 ) Total deferred income tax assets 2,001 1,772 Deferred income tax liabilities: U.S. federal and state intangible assets (2,131 ) (1,998 ) Non-U.S. goodwill and intangible assets (709 ) (602 ) Capitalized software (603 ) (530 ) Depreciation and amortization (266 ) (236 ) Prepaid expenses (152 ) (223 ) Outside basis in partnerships (300 ) (279 ) Other-non-U.S. (314 ) (86 ) Total deferred income tax liabilities (4,475 ) (3,954 ) Net deferred income tax liabilities $ (2,474 ) $ (2,182 )
Summary of Positions for which Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Table Text Block]	A reconciliation of the beginning and ending amount of unrecognized tax benefits as of December 31 is as follows: (in millions) 2018 2017 2016 Gross unrecognized tax benefits, beginning of period $ 598 $ 263 $ 224 Gross increases: Current year tax positions 487 356 37 Prior year tax positions 87 40 24 Gross decreases: Prior year tax positions (84 ) (33 ) (4 ) Settlements (20 ) (24 ) (6 ) Statute of limitations lapses (12 ) (4 ) (12 ) Gross unrecognized tax benefits, end of period $ 1,056 $ 598 $ 263

Shareholders' Equity (Tables)

Shareholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2018
Shareholders' Equity [Abstract]
Share Repurchase Activity	A summary of common share repurchases for the years ended December 31, 2018 and 2017 is as follows: Years Ended December 31, (in millions, except per share data) 2018 2017 Common share repurchases, shares 19 9 Common share repurchases, average price per share $ 236.72 $ 173.54 Common share repurchases, aggregate cost $ 4,500 $ 1,500 Board authorized shares remaining 94 42

Share-Based Compensation (Table

Share-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Option and SAR Activity [Table Text Block]	Stock option and SAR activity for the year ended December 31, 2018 is summarized in the table below: Shares Weighted- Average Exercise Price Weighted- Average Remaining Contractual Life Aggregate Intrinsic Value (in millions) (in years) (in millions) Outstanding at beginning of period 37 $ 102 Granted 7 229 Exercised (8 ) 78 Forfeited (1 ) 162 Outstanding at end of period 35 131 6.5 $ 4,114 Exercisable at end of period 16 87 5.0 2,560 Vested and expected to vest, end of period 34 129 6.5 4,072
Restricted Share Activity [Table Text Block]	Restricted share activity for the year ended December 31, 2018 is summarized in the table below: (shares in millions) Shares Weighted-Average Grant Date Fair Value per Share Nonvested at beginning of period 7 $ 128 Granted 2 229 Vested (3 ) 119 Nonvested at end of period 6 163
Other Share-Based Compensation Data [Table Text Block]	Other Share-Based Compensation Data (in millions, except per share amounts) For the Years Ended December 31, 2018 2017 2016 Stock Options and SARs Weighted-average grant date fair value of shares granted, per share $ 43 $ 29 $ 20 Total intrinsic value of stock options and SARs exercised 1,431 1,473 595 Restricted Shares Weighted-average grant date fair value of shares granted, per share 229 163 115 Total fair value of restricted shares vested $ 521 $ 460 $ 274 Employee Stock Purchase Plan Number of shares purchased 2 2 2 Share-Based Compensation Items Share-based compensation expense, before tax $ 638 $ 597 $ 485 Share-based compensation expense, net of tax effects 587 531 417 Income tax benefit realized from share-based award exercises 239 431 236 (in millions, except years) December 31, 2018 Unrecognized compensation expense related to share awards $ 628 Weighted-average years to recognize compensation expense 1.3
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]	The principal assumptions the Company used in calculating grant-date fair value for stock options and SARs were as follows: For the Years Ended December 31, 2018 2017 2016 Risk-free interest rate 2.6% - 3.1% 1.9% - 2.1% 1.2% - 1.4% Expected volatility 18.7% - 19.3% 18.5% - 20.7% 20.8% - 22.5% Expected dividend yield 1.3% - 1.5% 1.4% - 1.6% 1.8% Forfeiture rate 5.0% 5.0% 5.0% Expected life in years 5.6 5.7 5.6 - 5.9

Commitments and Contingencies_2

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2018
Operating Leased Assets [Line Items]
Lessee, Operating Lease, Disclosure [Table Text Block]	As of December 31, 2018 , future minimum annual lease payments, net of sublease income, under all non-cancelable operating leases were as follows: (in millions) Future Minimum Lease Payments 2019 $ 669 2020 592 2021 511 2022 423 2023 338 Thereafter 1,343

Segment Financial Information_2

Segment Financial Information (Tables)	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
Segment Financial Information [Table Text Block]	The following table presents the reportable segment financial information: Optum (in millions) UnitedHealthcare OptumHealth OptumInsight OptumRx Optum Eliminations Optum Corporate and Eliminations Consolidated 2018 Revenues - unaffiliated customers: Premiums $ 174,282 $ 3,805 $ — $ — $ — $ 3,805 $ — $ 178,087 Products — 52 111 29,438 — 29,601 — 29,601 Services 8,366 4,925 3,280 612 — 8,817 — 17,183 Total revenues - unaffiliated customers 182,648 8,782 3,391 30,050 — 42,223 — 224,871 Total revenues - affiliated customers — 14,882 5,596 39,440 (1,409 ) 58,509 (58,509 ) — Investment and other income 828 481 21 46 — 548 — 1,376 Total revenues $ 183,476 $ 24,145 $ 9,008 $ 69,536 $ (1,409 ) $ 101,280 $ (58,509 ) $ 226,247 Earnings from operations $ 9,113 $ 2,430 $ 2,243 $ 3,558 $ — $ 8,231 $ — $ 17,344 Interest expense — — — — — — (1,400 ) (1,400 ) Earnings before income taxes $ 9,113 $ 2,430 $ 2,243 $ 3,558 $ — $ 8,231 $ (1,400 ) $ 15,944 Total assets $ 82,938 $ 29,837 $ 11,039 $ 33,912 $ — $ 74,788 $ (5,505 ) $ 152,221 Purchases of property, equipment and capitalized software 761 593 517 192 — 1,302 — 2,063 Depreciation and amortization 845 439 654 490 — 1,583 — 2,428 2017 Revenues - unaffiliated customers: Premiums $ 154,709 $ 3,744 $ — $ — $ — $ 3,744 $ — $ 158,453 Products — 44 106 26,216 — 26,366 — 26,366 Services 7,890 4,013 2,849 565 — 7,427 — 15,317 Total revenues - unaffiliated customers 162,599 7,801 2,955 26,781 — 37,537 — 200,136 Total revenues - affiliated customers — 12,429 5,127 36,954 (1,227 ) 53,283 (53,283 ) — Investment and other income 658 340 5 20 — 365 — 1,023 Total revenues $ 163,257 $ 20,570 $ 8,087 $ 63,755 $ (1,227 ) $ 91,185 $ (53,283 ) $ 201,159 Earnings from operations $ 8,498 $ 1,823 $ 1,770 $ 3,118 $ — $ 6,711 $ — $ 15,209 Interest expense — — — — — — (1,186 ) (1,186 ) Earnings before income taxes $ 8,498 $ 1,823 $ 1,770 $ 3,118 $ — $ 6,711 $ (1,186 ) $ 14,023 Total assets $ 76,676 $ 26,931 $ 11,273 $ 29,551 $ — $ 67,755 $ (5,373 ) $ 139,058 Purchases of property, equipment and capitalized software 737 510 588 188 — 1,286 — 2,023 Depreciation and amortization 758 380 614 493 — 1,487 — 2,245 2016 Revenues - unaffiliated customers: Premiums $ 140,455 $ 3,663 $ — $ — $ — $ 3,663 $ — $ 144,118 Products 1 48 103 26,506 — 26,657 — 26,658 Services 7,514 2,498 2,670 554 — 5,722 — 13,236 Total revenues - unaffiliated customers 147,970 6,209 2,773 27,060 — 36,042 — 184,012 Total revenues - affiliated customers — 10,491 4,559 33,372 (1,088 ) 47,334 (47,334 ) — Investment and other income 611 208 1 8 — 217 — 828 Total revenues $ 148,581 $ 16,908 $ 7,333 $ 60,440 $ (1,088 ) $ 83,593 $ (47,334 ) $ 184,840 Earnings from operations $ 7,307 $ 1,428 $ 1,513 $ 2,682 $ — $ 5,623 $ — $ 12,930 Interest expense — — — — — — (1,067 ) (1,067 ) Earnings before income taxes $ 7,307 $ 1,428 $ 1,513 $ 2,682 $ — $ 5,623 $ (1,067 ) $ 11,863 Total assets $ 70,505 $ 18,656 $ 9,017 $ 29,066 $ — $ 56,739 $ (4,434 ) $ 122,810 Purchases of property, equipment and capitalized software 640 345 571 149 — 1,065 — 1,705 Depreciation and amortization 724 297 559 475 — 1,331 — 2,055

Quarterly Financial Data (Una_2

Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2018
Schedule of Quarterly Financial Information [Table Text Block]	Selected quarterly financial information for all quarters of 2018 and 2017 is as follows: For the Quarter Ended (in millions, except per share data) March 31 June 30 September 30 December 31 2018 Revenues $ 55,188 $ 56,086 $ 56,556 $ 58,417 Operating costs 51,135 51,882 51,966 53,920 Earnings from operations 4,053 4,204 4,590 4,497 Net earnings 2,924 3,010 3,284 3,164 Net earnings attributable to UnitedHealth Group common shareholders 2,836 2,922 3,188 3,040 Net earnings per share attributable to UnitedHealth Group common shareholders: Basic 2.94 3.04 3.31 3.16 Diluted 2.87 2.98 3.24 3.10 2017 Revenues $ 48,723 $ 50,053 $ 50,322 $ 52,061 Operating costs 45,310 46,322 46,234 48,084 Earnings from operations 3,413 3,731 4,088 3,977 Net earnings 2,191 2,350 2,561 3,721 Net earnings attributable to UnitedHealth Group common shareholders 2,172 2,284 2,485 3,617 Net earnings per share attributable to UnitedHealth Group common shareholders: Basic 2.28 2.37 2.57 3.73 Diluted 2.23 2.32 2.51 3.65

Schedule I (Tables)

Schedule I (Tables)	12 Months Ended
	Dec. 31, 2018
Condensed Financial Statements, Captions [Line Items]
Schedule of Maturities of Long-term Debt [Table Text Block]	Maturities of long-term debt for the years ending December 31 are as follows: (in millions) 2019 $ 1,973 2020 3,350 2021 3,350 2022 3,215 2023 2,325 Thereafter 22,775
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Condensed Balance Sheet [Table Text Block]	Condensed Financial Information of Registrant (Parent Company Only) UnitedHealth Group Condensed Balance Sheets (in millions, except per share data) December 31, December 31, Assets Current assets: Cash and cash equivalents $ 434 $ 359 Other current assets 197 575 Total current assets 631 934 Equity in net assets of subsidiaries 83,244 76,231 Long-term notes receivable from subsidiaries 4,461 4,278 Other assets 972 839 Total assets $ 89,308 $ 82,282 Liabilities and shareholders’ equity Current liabilities: Accounts payable and accrued liabilities $ 618 $ 502 Current portion of notes payable to subsidiaries 714 466 Commercial paper and current maturities of long-term debt 1,744 2,749 Total current liabilities 3,076 3,717 Long-term debt, less current maturities 33,490 28,318 Long-term notes payable to subsidiaries 560 1,518 Other liabilities 486 953 Total liabilities 37,612 34,506 Commitments and contingencies (Note 4) Shareholders’ equity: Preferred stock, $0.001 par value -10 shares authorized; no shares issued or outstanding — — Common stock, $0.01 par value - 3,000 shares authorized; 960 and 969 issued and outstanding 10 10 Additional paid-in capital — 1,703 Retained earnings 55,846 48,730 Accumulated other comprehensive loss (4,160 ) (2,667 ) Total UnitedHealth Group shareholders’ equity 51,696 47,776 Total liabilities and shareholders’ equity $ 89,308 $ 82,282
Condensed Statement of Comprehensive Income [Table Text Block]	Condensed Financial Information of Registrant (Parent Company Only) UnitedHealth Group Condensed Statements of Comprehensive Income For the Years Ended December 31, (in millions) 2018 2017 2016 Revenues: Investment and other income $ 194 $ 527 $ 522 Total revenues 194 527 522 Operating costs: Operating costs 35 — (22 ) Interest expense 1,285 1,114 995 Total operating costs 1,320 1,114 973 Loss before income taxes (1,126 ) (587 ) (451 ) Benefit for income taxes 251 214 165 Loss of parent company (875 ) (373 ) (286 ) Equity in undistributed income of subsidiaries 12,861 10,931 7,303 Net earnings 11,986 10,558 7,017 Other comprehensive (loss) income (1,517 ) 14 653 Comprehensive income $ 10,469 $ 10,572 $ 7,670
Condensed Cash Flow Statement [Table Text Block]	Condensed Financial Information of Registrant (Parent Company Only) UnitedHealth Group Condensed Statements of Cash Flows For the Years Ended December 31, (in millions) 2018 2017 2016 Operating activities Cash flows from operating activities $ 6,099 $ 2,021 $ 4,294 Investing activities Issuances of notes to subsidiaries (1,420 ) — (824 ) Repayments of notes to subsidiaries 1,419 2,071 — Cash paid for acquisitions (4,066 ) (2,313 ) (2,292 ) Return of capital to parent company 4,196 3,375 2,143 Capital contributions to subsidiaries (1,259 ) (959 ) (765 ) Other, net 4 — 168 Cash flows (used for) from investing activities (1,126 ) 2,174 (1,570 ) Financing activities Common stock repurchases (4,500 ) (1,500 ) (1,280 ) Proceeds from common stock issuances 838 688 429 Cash dividends paid (3,320 ) (2,773 ) (2,261 ) Repayments of commercial paper, net (201 ) (3,508 ) (382 ) Proceeds from issuance of long-term debt 6,935 5,291 3,968 Repayments of long-term debt (2,600 ) (3,472 ) (2,596 ) (Repayments) proceeds of notes from subsidiary (1,127 ) 1,704 (30 ) Other, net (923 ) (446 ) (421 ) Cash flows used for financing activities (4,898 ) (4,016 ) (2,573 ) Increase in cash and cash equivalents 75 179 151 Cash and cash equivalents, beginning of period 359 180 29 Cash and cash equivalents, end of period $ 434 $ 359 $ 180 Supplemental cash flow disclosures Cash paid for interest $ 1,294 $ 1,062 $ 974 Cash paid for income taxes 2,379 3,455 4,557 Supplemental schedule of non-cash investing activities Common stock issued for acquisitions $ — $ 2,164 $ — Conversion of note receivable from subsidiaries to equity — 4,378 —
Schedule of Maturities of Long-term Debt [Table Text Block]	Maturities of commercial paper and long-term debt for the years ending December 31 are as follows: (in millions) 2019 $ 1,750 2020 3,150 2021 3,150 2022 3,015 2023 2,125 Thereafter 22,477

Basis of Presentation, Uses o_4

Basis of Presentation, Uses of Estimates and Significant Accounting Policies (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)	Jan. 01, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2015USD ($)
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets		$ 24	$ 0	$ 28
Accounts payable and accrued liabilities	$ 16,705		15,180
Other current receivables	6,862		6,262
Goodwill, Impairment Loss	0
Impairment of Intangible Assets (Excluding Goodwill)	$ 0
Number Of Days Notice Required To Cancel Health Insurance Contract	30 days
Accounts Receivable, Net, Current	$ 11,388		9,568
Other Liabilities, Current	12,244		12,286
Other Current Liabilities [Member]
Health savings account deposits	$ 7,500		6,400
Restricted Stock [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	2 years
Restricted Stock [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	5 years
Stock Options and SARs [Member] [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	4 years
Share-based Compensation Arrangement by Share-based Payment Plan Award, Options, Award Exercisable Period	10 years
Employee Stock Purchase Plan (ESPP) [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Discount from Market Price, Offering Date	85.00%
Accounting Standards Update 2016-02 [Member]
New Accounting Pronouncement or Change in Accounting Principle, Description of Transition Method	Cumulative effect upon adoption approach
New Accounting Pronouncement, Transition Guidance Not Significant or Not Practical	Impact is not material
Accounting Standards Update 2016-01 [Member]
New Accounting Pronouncement or Change in Accounting Principle, Description of Transition Method	Prospective
Health Insurance Product Line [Member]
Short-duration Insurance Contracts, Historical Claims Duration, First 90 Days	0.9
Products and services [Member]
Accounts Receivable, Net, Current	$ 3,900		3,700
Pharmaceutical Manufacturer Rebates Receivable [Member]
Other current receivables	$ 4,200		$ 3,800

Basis of Presentation, Uses o_5

Basis of Presentation, Uses of Estimates and Significant Accounting Policies Useful lives for property, equipment and capitalized software (Details)	12 Months Ended
	Dec. 31, 2018
Furniture, Fixtures and equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Useful Life	3 years
Furniture, Fixtures and equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Useful Life	10 years
Buildings [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Useful Life	35 years
Buildings [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Useful Life	40 years
Capitalized software [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Useful Life	3 years
Capitalized software [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Useful Life	5 years

Basis of Presentation, Uses o_6

Basis of Presentation, Uses of Estimates and Significant Accounting Policies Redeemable Noncontrolling Interests (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Noncontrolling Interest [Line Items]
Redeemable noncontrolling interest, beginning of period	$ 2,189
Acquisitions	521	$ 2,112
Redemptions		283	$ (143)
Distributions	(228)	(152)	(32)
Fair value and other adjustments	163	(113)	216
Redeemable Noncontrolling Interest, end of period	1,908	2,189
Redeemable Noncontrolling Interests [Member]
Noncontrolling Interest [Line Items]
Redeemable noncontrolling interest, beginning of period	2,189	2,012
Net earnings	123	71
Acquisitions	102	565
Redemptions	(90)	(309)
Distributions	(53)	(38)
Fair value and other adjustments	(363)	(112)
Redeemable Noncontrolling Interest, end of period	$ 1,908	$ 2,189	$ 2,012

Investments (Narrative) (Detail

Investments (Narrative) (Details) $ in Millions	Dec. 31, 2018USD ($)positions	Dec. 31, 2017USD ($)
Investment [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | positions	19,000
Total number of security positions	31,000
Available-for-sale Securities, Equity Securities		$ 1,992
Equity Securities, FV-NI and without Readily Determinable Fair Value	$ 2,000
Equity Method Investments	$ 1,500	$ 900

Investments (Short-Term and Lon

Investments (Short-Term and Long-Term Investments) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 32,240	$ 28,410
Securities, Available for sale Debt Securities, Gross Unrealized Gains	101	167
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(443)	(153)
Debt Securities, Available-for-sale	31,898	28,424
Held-to-maturity securities, Amortized Cost	621	536
Securities, Held to maturity, Unrecognized Holding Gain	1	1
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(2)	(1)
Debt Securities, Held-to-maturity, Fair Value	620	536
Total investments, Amortized Cost	32,861	28,946
Total investments, Gross Unrealized Gains	102	168
Total investments, Gross Unrealized Losses	(445)	(154)
Investments, Fair Value Disclosure	32,518	28,960
Debt Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale	31,898	28,424
U.S. Government and Agency Obligations [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	3,434	2,673
Securities, Available for sale Debt Securities, Gross Unrealized Gains	13	1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(42)	(30)
Debt Securities, Available-for-sale	3,405	2,644
Held-to-maturity securities, Amortized Cost	255	254
Securities, Held to maturity, Unrecognized Holding Gain	1	1
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(2)	(1)
Debt Securities, Held-to-maturity, Fair Value	254	254
State and Municipal Obligations [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	7,117	7,596
Securities, Available for sale Debt Securities, Gross Unrealized Gains	61	99
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(57)	(35)
Debt Securities, Available-for-sale	7,121	7,660
Held-to-maturity securities, Amortized Cost	11	2
Securities, Held to maturity, Unrecognized Holding Gain	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	0
Debt Securities, Held-to-maturity, Fair Value	11	2
Corporate Obligations [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	15,366	13,181
Securities, Available for sale Debt Securities, Gross Unrealized Gains	14	57
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(218)	(44)
Debt Securities, Available-for-sale	15,162	13,194
Held-to-maturity securities, Amortized Cost	355	280
Securities, Held to maturity, Unrecognized Holding Gain	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	0
Debt Securities, Held-to-maturity, Fair Value	355	280
U.S. Agency Mortgage-Backed Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	4,947	3,942
Securities, Available for sale Debt Securities, Gross Unrealized Gains	11	7
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(106)	(38)
Debt Securities, Available-for-sale	4,852	3,911
Non-U.S. Agency Mortgage-Backed Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	1,376	1,018
Securities, Available for sale Debt Securities, Gross Unrealized Gains	2	3
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(20)	(6)
Debt Securities, Available-for-sale	$ 1,358	$ 1,015

Investments (Amortized Cost and

Investments (Amortized Cost and Fair Value of Available-for-Sale Debt Securities by Contractual Maturity) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Schedule of Investments [Line Items]
Due in one year or less, Amortized Cost	$ 3,560
Due after one year through five years, Amortized Cost	12,432
Due after five years through ten years, Amortized Cost	7,362
Due after ten years, Amortized Cost	2,563
Total debt securities - available-for-sale, Amortized Cost	32,240	$ 28,410
Due in one year or less, Fair Value	3,551
Due after one year through five years, Fair Value	12,297
Due after five years through ten years, Fair Value	7,270
Due after ten years, Fair Value	2,570
Debt Securities, Available-for-sale	31,898	28,424
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, within One Year, Amortized Cost	150
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, within One Year, Fair Value	150
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Amortized Cost	213
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Fair Value	212
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Amortized Cost	129
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Fair Value	129
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after 10 Years, Amortized Cost	129
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after 10 Years, Fair Value	129
Debt Securities, Held-to-maturity	621	536
Debt Securities, Held-to-maturity, Fair Value	620	536
U.S. Agency Mortgage-Backed Securities [Member]
Schedule of Investments [Line Items]
Mortgage-backed securities, Amortized Cost	4,947
Total debt securities - available-for-sale, Amortized Cost	4,947	3,942
Debt Securities, Available-for-sale	4,852	3,911
Mortgage-backed securities, Fair Value	4,852
Non-U.S. Agency Mortgage-Backed Securities [Member]
Schedule of Investments [Line Items]
Mortgage-backed securities, Amortized Cost	1,376
Total debt securities - available-for-sale, Amortized Cost	1,376	1,018
Debt Securities, Available-for-sale	1,358	$ 1,015
Mortgage-backed securities, Fair Value	$ 1,358

Investments (Fair Value of Avai

Investments (Fair Value of Available-For-Sale Investments with Gross Unrealized Losses by Investment Type and Length of Time That Individual Securities Have Been in a Continuous Unrealized Loss Position) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Debt Securities [Member]
Schedule of Investments [Line Items]
Less Than 12 Months, Fair Value	$ 12,355	$ 11,817
Less Than 12 Months, Gross Unrealized Losses	(156)	(67)
Greater Than 12 Months, Fair Value	11,002	4,441
Greater Than 12 Months, Gross Unrealized Losses	(287)	(86)
Total, Fair Value	23,357	16,258
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(443)	(153)
U.S. Government and Agency Obligations [Member]
Schedule of Investments [Line Items]
Less Than 12 Months, Fair Value	998	1,249
Less Than 12 Months, Gross Unrealized Losses	(7)	(8)
Greater Than 12 Months, Fair Value	1,425	1,027
Greater Than 12 Months, Gross Unrealized Losses	(35)	(22)
Total, Fair Value	2,423	2,276
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(42)	(30)
State and Municipal Obligations [Member]
Schedule of Investments [Line Items]
Less Than 12 Months, Fair Value	1,334	2,599
Less Than 12 Months, Gross Unrealized Losses	(11)	(21)
Greater Than 12 Months, Fair Value	2,491	866
Greater Than 12 Months, Gross Unrealized Losses	(46)	(14)
Total, Fair Value	3,825	3,465
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(57)	(35)
Corporate Obligations [Member]
Schedule of Investments [Line Items]
Less Than 12 Months, Fair Value	8,105	5,901
Less Than 12 Months, Gross Unrealized Losses	(109)	(23)
Greater Than 12 Months, Fair Value	4,239	1,242
Greater Than 12 Months, Gross Unrealized Losses	(109)	(21)
Total, Fair Value	12,344	7,143
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(218)	(44)
U.S. Agency Mortgage-Backed Securities [Member]
Schedule of Investments [Line Items]
Less Than 12 Months, Fair Value	1,296	1,657
Less Than 12 Months, Gross Unrealized Losses	(22)	(12)
Greater Than 12 Months, Fair Value	2,388	1,162
Greater Than 12 Months, Gross Unrealized Losses	(84)	(26)
Total, Fair Value	3,684	2,819
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(106)	(38)
Non-U.S. Agency Mortgage-Backed Securities [Member]
Schedule of Investments [Line Items]
Less Than 12 Months, Fair Value	622	411
Less Than 12 Months, Gross Unrealized Losses	(7)	(3)
Greater Than 12 Months, Fair Value	459	144
Greater Than 12 Months, Gross Unrealized Losses	(13)	(3)
Total, Fair Value	1,081	555
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ (20)	$ (6)

Fair Value (Narrative) (Details

Fair Value (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Fair Value [Line Items]
Transfers Into Level 3	$ 0	$ 0
Transfers out of Level 3	0	0
Fair Value, Measurements, Nonrecurring [Member]
Fair Value [Line Items]
Significant fair value adjustments for assets and liabilities measured on a nonrecurring basis	$ 0	$ 0

Fair Value (Financial Assets an

Fair Value (Financial Assets and Liabilities, Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	$ 10,866	$ 11,981
Debt Securities, Available-for-sale	31,898	28,424
Equity Securities, FV-NI	1,845
Available-for-sale Securities, Equity Securities		1,992
Assets under management	3,032	3,101
Assets, Fair Value Disclosure	47,641	45,498
Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	31,898	28,424
U.S. Government and Agency Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	3,405	2,644
State and Municipal Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	7,121	7,660
Corporate Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	15,162	13,194
U.S. Agency Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	4,852	3,911
Non-U.S. Agency Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	1,358	1,015
Quoted Prices in Active Markets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	10,757	11,718
Equity Securities, FV-NI	1,832
Available-for-sale Securities, Equity Securities		1,784
Assets under management	1,086	1,117
Assets, Fair Value Disclosure	16,774	17,112
Quoted Prices in Active Markets (Level 1) [Member] | Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	3,099	2,493
Quoted Prices in Active Markets (Level 1) [Member] | U.S. Government and Agency Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	3,060	2,428
Quoted Prices in Active Markets (Level 1) [Member] | State and Municipal Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	0	0
Quoted Prices in Active Markets (Level 1) [Member] | Corporate Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	39	65
Quoted Prices in Active Markets (Level 1) [Member] | U.S. Agency Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	0	0
Quoted Prices in Active Markets (Level 1) [Member] | Non-U.S. Agency Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	0	0
Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	109	263
Equity Securities, FV-NI	13
Available-for-sale Securities, Equity Securities		14
Assets under management	1,938	1,984
Assets, Fair Value Disclosure	30,686	28,052
Other Observable Inputs (Level 2) [Member] | Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	28,626	25,791
Other Observable Inputs (Level 2) [Member] | U.S. Government and Agency Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	345	216
Other Observable Inputs (Level 2) [Member] | State and Municipal Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	7,121	7,660
Other Observable Inputs (Level 2) [Member] | Corporate Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	14,950	12,989
Other Observable Inputs (Level 2) [Member] | U.S. Agency Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	4,852	3,911
Other Observable Inputs (Level 2) [Member] | Non-U.S. Agency Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	1,358	1,015
Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0
Equity Securities, FV-NI	0
Available-for-sale Securities, Equity Securities		194
Assets under management	8	0
Assets, Fair Value Disclosure	181	334
Unobservable Inputs (Level 3) [Member] | Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	173	140
Unobservable Inputs (Level 3) [Member] | U.S. Government and Agency Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	0	0
Unobservable Inputs (Level 3) [Member] | State and Municipal Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	0	0
Unobservable Inputs (Level 3) [Member] | Corporate Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	173	140
Unobservable Inputs (Level 3) [Member] | U.S. Agency Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	0	0
Unobservable Inputs (Level 3) [Member] | Non-U.S. Agency Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	$ 0	$ 0

Fair Value (Financial Assets _2

Fair Value (Financial Assets and Liabilities, Not Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Held-to-maturity, Fair Value	$ 620	$ 536
Debt Securities, Held-to-maturity	621	536
Debt and other financing obligations, carrying value	35,234	31,067
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Held-to-maturity, Fair Value	620	536
Fair Value, Measurements, Nonrecurring [Member] | Quoted Prices in Active Markets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Held-to-maturity, Fair Value	260	267
Fair Value, Measurements, Nonrecurring [Member] | Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Held-to-maturity, Fair Value	65	4
Fair Value, Measurements, Nonrecurring [Member] | Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Held-to-maturity, Fair Value	295	265
Long-term debt and other financing obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt and other financing obligations, carrying value	36,554	31,542
Long-term debt and other financing obligations [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt and other financing obligations	37,944	34,504
Long-term debt and other financing obligations [Member] | Fair Value, Measurements, Nonrecurring [Member] | Quoted Prices in Active Markets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt and other financing obligations	0	0
Long-term debt and other financing obligations [Member] | Fair Value, Measurements, Nonrecurring [Member] | Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt and other financing obligations	37,944	34,504
Long-term debt and other financing obligations [Member] | Fair Value, Measurements, Nonrecurring [Member] | Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt and other financing obligations	$ 0	$ 0

Property, Plant, and Capitali_3

Property, Plant, and Capitalized Software (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Depreciation	$ 924	$ 799	$ 698
Capitalized Computer Software, Amortization	$ 606	$ 550	$ 475

Property, Plant, and Capitali_4

Property, Plant, and Capitalized Software Property Plant and Equipment Table (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Land and improvements	$ 566	$ 405
Buildings and improvements	4,470	3,664
Computer equipment	1,984	1,829
Furniture and fixtures	1,525	1,208
Less accumulated depreciation	(2,787)	(2,488)
Property and equipment, net	5,758	4,618
Capitalized software	4,054	3,601
Less accumulated amortization	(1,354)	(1,206)
Capitalized software, net	2,700	2,395
Total property, equipment and capitalized software, net	$ 8,458	$ 7,013

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Amortization of Intangible Assets	$ 898	$ 896	$ 882

Goodwill and Intangible Asset_4

Goodwill and Intangible Assets Changes in the Carrying Amount of Goodwill by Reporting Segment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Goodwill [Line Items]
Goodwill, Beginning Balance	$ 54,556	$ 47,584
Acquisitions	5,181	7,100
Foreign currency effects and adjustments, net	(827)	(128)
Goodwill, Ending Balance	58,910	54,556
UnitedHealthcare
Goodwill [Line Items]
Goodwill, Beginning Balance	24,484	23,854
Acquisitions	2,723	690
Foreign currency effects and adjustments, net	(807)	(60)
Goodwill, Ending Balance	26,400	24,484
OptumHealth
Goodwill [Line Items]
Goodwill, Beginning Balance	11,488	6,322
Acquisitions	471	5,189
Foreign currency effects and adjustments, net	(12)	(23)
Goodwill, Ending Balance	11,947	11,488
OptumInsight
Goodwill [Line Items]
Goodwill, Beginning Balance	5,674	4,449
Acquisitions	106	1,221
Foreign currency effects and adjustments, net	(8)	4
Goodwill, Ending Balance	5,772	5,674
OptumRx
Goodwill [Line Items]
Goodwill, Beginning Balance	12,910	12,959
Acquisitions	1,881	0
Foreign currency effects and adjustments, net	0	(49)
Goodwill, Ending Balance	$ 14,791	$ 12,910

Goodwill and Intangible Asset_5

Goodwill and Intangible Assets Gross carrying value, accumulated amortization and net carrying value of intangible assets (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Intangible Assets [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	$ 13,917	$ 12,798
Finite-Lived Intangible Assets, Accumulated Amortization	(4,592)	(4,309)
Intangible Assets, Net (Excluding Goodwill)	9,325	8,489
Customer-Related Intangible Assets [Member]
Intangible Assets [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	11,622	10,832
Finite-Lived Intangible Assets, Accumulated Amortization	(3,908)	(3,743)
Intangible Assets, Net (Excluding Goodwill)	7,714	7,089
Trademarks and Technology [Member]
Intangible Assets [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	1,122	1,054
Finite-Lived Intangible Assets, Accumulated Amortization	(512)	(432)
Intangible Assets, Net (Excluding Goodwill)	610	622
Trademarks and Trade Names [Member]
Intangible Assets [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	745	561
Finite-Lived Intangible Assets, Accumulated Amortization	0	0
Intangible Assets, Net (Excluding Goodwill)	745	561
Other Intangible Assets [Member]
Intangible Assets [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	428	351
Finite-Lived Intangible Assets, Accumulated Amortization	(172)	(134)
Intangible Assets, Net (Excluding Goodwill)	$ 256	$ 217

Goodwill and Intangible Asset_6

Goodwill and Intangible Assets Weighted-average useful lives assigned to finite-lived intangible assets acquired in business combinations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired	$ 1,574	$ 773
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	16 years	11 years
Customer-Related Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired	$ 1,355	$ 324
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	17 years	13 years
Trademarks and Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired	$ 122	$ 367
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	4 years	11 years
Other Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired	$ 97	$ 82
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	9 years	6 years

Goodwill and Intangible Asset_7

Goodwill and Intangible Assets Amortization Expense relating to Intangible Assets (Details) $ in Millions	Dec. 31, 2018USD ($)
Finite-Lived Intangible Assets [Line Items]
2,019	$ 889
2,020	795
2,021	724
2,022	632
2,023	$ 593

Medical Costs Payable (Narrativ

Medical Costs Payable (Narrative) (Details) - USD ($) $ in Billions	Dec. 31, 2018	Dec. 31, 2017
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred but Not Reported (IBNR) Claims, Amount	$ 13.2	$ 12.3

Medical Costs Payable Rollforwa

Medical Costs Payable Rollforward (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Medical costs payable, beginning of period	$ 17,871	$ 16,391	$ 14,330
Acquisitions	339	83	0
Reported medical costs:
Current year	145,723	130,726	117,258
Prior years	(320)	(690)	(220)
Total reported medical costs	145,403	130,036	117,038
Medical payments:
Payments for current year	(127,155)	(113,811)	(101,696)
Payments for prior years	(16,567)	(14,828)	(13,281)
Total medical payments	(143,722)	(128,639)	(114,977)
Medical costs payable, end of period	$ 19,891	$ 17,871	$ 16,391

Medical Costs Payable, Incurred

Medical Costs Payable, Incurred and Paid Medical Cost Development (Details) - Health Insurance Product Line [Member] - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Net Incurred Medical Costs	$ 276,164
Net Cumulative Medical Payments	(256,933)
Net remaining outstanding liabilities prior to 2017	660
Total Medical costs payable	19,891
Short-duration Insurance Contracts, Accident Year 2017 [Member]
Net Incurred Medical Costs	130,441	$ 130,726
Net Cumulative Medical Payments	(129,778)	$ (113,811)
Short-duration Insurance Contracts, Accident Year 2018 [Member]
Net Incurred Medical Costs	145,723
Net Cumulative Medical Payments	$ (127,155)

Commercial Paper and Long-Ter_3

Commercial Paper and Long-Term Debt (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Minimum [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate During Period	3.20%
Maximum [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate During Period	3.60%
Five Year $3.5 Billion Credit Facility [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Long-term Line of Credit	$ 0
Line of Credit, Credit Facility, Maximum Borrowing Capacity	$ 3,500
Maturity Period, Line of Credit	5 years
Three Year $3.5 Billion Credit Facility [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Long-term Line of Credit	$ 0
Line of Credit, Credit Facility, Maximum Borrowing Capacity	$ 3,500
Maturity Period, Line of Credit	3 years
364 Day $3.0 Billion Credit Facility [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Long-term Line of Credit	$ 0
Line of Credit, Credit Facility, Maximum Borrowing Capacity	$ 3,000
Maturity Period, Line of Credit	364 days
Subsidiaries [Member]
Debt Instrument [Line Items]
Other Long-term Debt	$ 1,300	$ 625
Other Long-term Debt, Current	$ 229	$ 107

Commercial Paper and Long-Ter_4

Commercial Paper and Long-Term Debt (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Par Value	$ 35,667	$ 31,417
Carrying Value	35,234	31,067
Fair Value	36,591	34,029
Commercial Paper [Member]
Debt Instrument [Line Items]
Par Value	0	150
Commercial Paper	0	150
Fair Value	$ 0	150
6.000% Notes Due February 2018 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	6.00%
Par Value	$ 0	1,100
Unsecured Debt, Current	0	1,101
Fair Value	$ 0	1,106
1.900% Notes Due July 2018 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.90%
Par Value	$ 0	1,500
Unsecured Debt, Current	0	1,499
Fair Value	$ 0	1,501
1.700% Notes due February 2019 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.70%
Par Value	$ 750	750
Unsecured Long-term Debt, Noncurrent		749
Unsecured Debt, Current	750
Fair Value	$ 749	747
1.625% Notes Due March 2019 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.625%
Par Value	$ 500	500
Unsecured Long-term Debt, Noncurrent		501
Unsecured Debt, Current	500
Fair Value	$ 499	497
2.300% Notes Due December 2019 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.30%
Par Value	$ 500	500
Unsecured Long-term Debt, Noncurrent		495
Unsecured Debt, Current	494
Fair Value	$ 497	501
2.700% Notes Due July 2020 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.70%
Par Value	$ 1,500	1,500
Unsecured Long-term Debt, Noncurrent	1,498	1,496
Fair Value	1,494	1,517
Floating rate notes due October 2020 [Member]
Debt Instrument [Line Items]
Par Value	300	300
Unsecured Long-term Debt, Noncurrent	299	299
Fair Value	$ 298	300
3.875% Notes Due October 2020 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.875%
Par Value	$ 450	450
Unsecured Long-term Debt, Noncurrent	443	446
Fair Value	$ 456	467
1.950% notes due October 2020 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.95%
Par Value	$ 900	900
Unsecured Long-term Debt, Noncurrent	897	895
Fair Value	$ 884	892
4.700% Notes Due February 2021 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.70%
Par Value	$ 400	400
Unsecured Long-term Debt, Noncurrent	398	403
Fair Value	$ 412	425
2.125% notes due March 2021 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.125%
Par Value	$ 750	750
Unsecured Long-term Debt, Noncurrent	747	746
Fair Value	734	744
Floating rate notes due June 2021 [Member]
Debt Instrument [Line Items]
Par Value	350	0
Unsecured Long-term Debt, Noncurrent	349	0
Fair Value	$ 347	0
3.150% notes due June 2021 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.15%
Par Value	$ 400	0
Unsecured Long-term Debt, Noncurrent	399	0
Fair Value	$ 400	0
3.375% Notes Due November 2021 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.375%
Par Value	$ 500	500
Unsecured Long-term Debt, Noncurrent	489	493
Fair Value	$ 503	516
2.875% Notes Due December 2021 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.875%
Par Value	$ 750	750
Unsecured Long-term Debt, Noncurrent	735	741
Fair Value	$ 748	760
2.875% Notes Due March 2022 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.875%
Par Value	$ 1,100	1,100
Unsecured Long-term Debt, Noncurrent	1,051	1,054
Fair Value	$ 1,091	1,114
3.350% Notes Due July 2022 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.35%
Par Value	$ 1,000	1,000
Unsecured Long-term Debt, Noncurrent	997	996
Fair Value	$ 1,005	1,033
2.375% notes due October 2022 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.375%
Par Value	$ 900	900
Unsecured Long-term Debt, Noncurrent	894	893
Fair Value	$ 872	891
0.000% Notes Due November 2022 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	0.00%
Par Value	$ 15	15
Unsecured Long-term Debt, Noncurrent	12	12
Fair Value	$ 13	12
2.750% Notes Due February 2023 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.75%
Par Value	$ 625	625
Unsecured Long-term Debt, Noncurrent	602	606
Fair Value	$ 611	626
2.875% Notes Due March 2023 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.875%
Par Value	$ 750	750
Unsecured Long-term Debt, Noncurrent	750	762
Fair Value	$ 739	759
3.500% notes due June 2023 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.50%
Par Value	$ 750	0
Unsecured Long-term Debt, Noncurrent	746	0
Fair Value	$ 756	0
3.500% notes due February 2024 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.50%
Par Value	$ 750	0
Unsecured Long-term Debt, Noncurrent	745	0
Fair Value	$ 755	0
3.750% Notes Due July 2025 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.75%
Par Value	$ 2,000	2,000
Unsecured Long-term Debt, Noncurrent	1,989	1,987
Fair Value	$ 2,025	2,108
3.700% notes due December 2025 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.70%
Par Value	$ 300	0
Unsecured Long-term Debt, Noncurrent	298	0
Fair Value	$ 303	0
3.100% notes due March 2026 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.10%
Par Value	$ 1,000	1,000
Unsecured Long-term Debt, Noncurrent	995	995
Fair Value	$ 965	1,007
3.450% notes due January 2027 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.45%
Par Value	$ 750	750
Unsecured Long-term Debt, Noncurrent	746	745
Fair Value	$ 742	776
3.375% notes due April 2027 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.375%
Par Value	$ 625	625
Unsecured Long-term Debt, Noncurrent	619	618
Fair Value	$ 611	642
2.950% notes due October 2027 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.95%
Par Value	$ 950	950
Unsecured Long-term Debt, Noncurrent	938	937
Fair Value	$ 898	947
3.850% notes due June 2028 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.85%
Par Value	$ 1,150	0
Unsecured Long-term Debt, Noncurrent	1,142	0
Fair Value	$ 1,163	0
3.875% notes due December 2028 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.875%
Par Value	$ 850	0
Unsecured Long-term Debt, Noncurrent	842	0
Fair Value	$ 861	0
4.625% Notes Due July 2035 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.625%
Par Value	$ 1,000	1,000
Unsecured Long-term Debt, Noncurrent	992	991
Fair Value	$ 1,060	1,165
5.800% Notes Due March 2036 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.80%
Par Value	$ 850	850
Unsecured Long-term Debt, Noncurrent	838	837
Fair Value	$ 1,003	1,105
6.500% Notes Due June 2037 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	6.50%
Par Value	$ 500	500
Unsecured Long-term Debt, Noncurrent	492	491
Fair Value	$ 638	698
6.625% Notes due November 2037 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	6.625%
Par Value	$ 650	650
Unsecured Long-term Debt, Noncurrent	641	641
Fair Value	$ 841	923
6.875% Notes Due Februray 2038 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	6.875%
Par Value	$ 1,100	1,100
Unsecured Long-term Debt, Noncurrent	1,076	1,075
Fair Value	$ 1,437	1,596
5.700% Notes Due October 2040 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.70%
Par Value	$ 300	300
Unsecured Long-term Debt, Noncurrent	296	296
Fair Value	$ 355	389
5.950% Notes Due Februrary 2041 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.95%
Par Value	$ 350	350
Unsecured Long-term Debt, Noncurrent	345	345
Fair Value	$ 426	466
4.625% Notes Due November 2041 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.625%
Par Value	$ 600	600
Unsecured Long-term Debt, Noncurrent	588	588
Fair Value	$ 627	685
4.375% Notes Due March 2042 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.375%
Par Value	$ 502	502
Unsecured Long-term Debt, Noncurrent	484	483
Fair Value	$ 503	555
3.950% Notes Due October 2042 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.95%
Par Value	$ 625	625
Unsecured Long-term Debt, Noncurrent	607	607
Fair Value	$ 596	650
4.250% Notes Due March 2043 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.25%
Par Value	$ 750	750
Unsecured Long-term Debt, Noncurrent	734	734
Fair Value	$ 744	822
4.750% Notes Due July 2045 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.75%
Par Value	$ 2,000	2,000
Unsecured Long-term Debt, Noncurrent	1,973	1,972
Fair Value	$ 2,116	2,362
4.200% notes due January 2047 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.20%
Par Value	$ 750	750
Unsecured Long-term Debt, Noncurrent	738	738
Fair Value	$ 745	808
4.250% notes due April 2047 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.25%
Par Value	$ 725	725
Unsecured Long-term Debt, Noncurrent	717	717
Fair Value	$ 719	798
3.750% notes due October 2047 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.75%
Par Value	$ 950	950
Unsecured Long-term Debt, Noncurrent	933	933
Fair Value	$ 869	969
4.250% notes due June 2048 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.25%
Par Value	$ 1,350	0
Unsecured Long-term Debt, Noncurrent	1,329	0
Fair Value	$ 1,349	0
4.450% notes due December 2048 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.45%
Par Value	$ 1,100	0
Unsecured Long-term Debt, Noncurrent	1,087	0
Fair Value	$ 1,132	$ 0

Commercial Paper and Long-Ter_5

Commercial Paper and Long-Term Debt Maturities of commercial paper and long-term debt (Details) $ in Millions	Dec. 31, 2018USD ($)
Debt Instrument [Line Items]
2,019	$ 1,973
2,020	3,350
2,021	3,350
2,022	3,215
2,023	2,325
Thereafter	$ 22,775

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	$ 6	$ 14	$ 11
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued	95	$ 84
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit	118
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	$ 716
Federal [Member] | Earliest Tax Year [Member]
Income Tax Contingency [Line Items]
Net Operating Loss Carryforwards, Expiration Date	Jan. 1, 2022
Open Tax Year	2,017
Federal [Member] | Latest Tax Year [Member]
Income Tax Contingency [Line Items]
Net Operating Loss Carryforwards, Expiration Date	Dec. 31, 2037
Open Tax Year	2,018
State [Member] | Earliest Tax Year [Member]
Income Tax Contingency [Line Items]
Net Operating Loss Carryforwards, Expiration Date	Jan. 1, 2019
Open Tax Year	2,013
State [Member] | Latest Tax Year [Member]
Income Tax Contingency [Line Items]
Net Operating Loss Carryforwards, Expiration Date	Dec. 31, 2038
Open Tax Year	2,018
Non-U.S [Member] | Earliest Tax Year [Member]
Income Tax Contingency [Line Items]
Open Tax Year	2,013
Non-U.S [Member] | Latest Tax Year [Member]
Income Tax Contingency [Line Items]
Open Tax Year	2,018
Finite-lived NOL carryforwards [Member] | Federal [Member]
Income Tax Contingency [Line Items]
Operating Loss Carryforwards	$ 99
Indefinite NOL carryforwards [Member] | Federal [Member]
Income Tax Contingency [Line Items]
Operating Loss Carryforwards	$ 17

Income Taxes Reconciliation of

Income Taxes Reconciliation of Provision for Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current Provision:
Federal	$ 2,897	$ 3,597	$ 4,302
State and local	219	314	312
Foreign	404	254	95
Total current provision	3,520	4,165	4,709
Deferred provision (benefit)	42	(965)	81
Total provision for income taxes	$ 3,562	$ 3,200	$ 4,790

Income Tax Reconciliation of th

Income Tax Reconciliation of the tax provision at the U.S. Federal Statutory Rate (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Contingency [Line Items]
Tax provision at the U.S. federal statutory rate, Amount	$ 3,348	$ 4,908	$ 4,152
Tax provision at the U.S. federal statutory rate, Percent	21.00%	35.00%	35.00%
Change in tax law, Amount	$ 0	$ (1,199)	$ 0
Change in tax law, Percent	0.00%	(8.60%)	0.00%
State income taxes, net of federal benefit, Amount	$ 168	$ 197	$ 205
State income taxes, net of federal benefit, Percent	1.00%	1.40%	1.70%
Share-based awards - excess tax benefit, Amount	$ (161)	$ (319)	$ (158)
Share-based awards - excess tax benefit, Percent	(1.00%)	(2.30%)	(1.30%)
Non-deductible compensation, Amount	$ 117	$ 175	$ 128
Non-deductible compensation, Percent	0.70%	1.30%	1.10%
Health insurance industry tax, Amount	$ 552	$ 0	$ 645
Health insurance industry tax, Percent	3.50%	0.00%	5.40%
Foreign rate differential, Amount	$ (203)	$ (282)	$ (105)
Foreign rate differential, Percent	(1.30%)	(2.00%)	(0.90%)
Other, net, Amount	$ (259)	$ (280)	$ (77)
Other, net, Percent	(1.60%)	(2.00%)	(0.60%)
Total provision for income taxes	$ 3,562	$ 3,200	$ 4,790
Provision for income taxes, Percent	22.30%	22.80%	40.40%

Income Taxes Components of Defe

Income Taxes Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Deferred income tax assets:
Accrued expenses and allowances	$ 551	$ 544
U.S. federal and state net operating loss carryforwards	190	216
Share-based compensation	91	97
Nondeductible liabilities	184	169
Non-U.S. tax loss carryforwards	426	445
Other-domestic	306	167
Other-non-U.S.	337	198
Subtotal	2,085	1,836
Less: valuation allowances	(84)	(64)
Total deferred income tax assets	2,001	1,772
Deferred income tax liabilities:
U.S. federal and state intangible assets	(2,131)	(1,998)
Non-U.S. goodwill and intangible assets	(709)	(602)
Capitalized software	(603)	(530)
Depreciation and amortization	(266)	(236)
Prepaid expenses	(152)	(223)
Outside basis in partnerships	(300)	(279)
Other-non-U.S.	(314)	(86)
Total deferred income tax liabilities	(4,475)	(3,954)
Net deferred income tax liabilities	$ (2,474)	$ (2,182)

Income Taxes Reconciliation o_2

Income Taxes Reconciliation of the beginning and ending amount of unrecognized tax benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Contingency [Line Items]
Gross unrecognized tax benefits, beginning of period	$ 598	$ 263	$ 224
Current year tax positions	487	356	37
Prior year tax positions, gross increases	87	40	24
Prior year tax positions, gross decreases	(84)	(33)	(4)
Settlements	(20)	(24)	(6)
Statute of limitations lapses	(12)	(4)	(12)
Gross unrecognized tax benefits, end of period	$ 1,056	$ 598	$ 263

Shareholders' Equity (Narrative

Shareholders' Equity (Narrative) (Details) - USD ($) shares in Millions, $ in Billions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Jun. 01, 2018
Shareholders' Equity Disclosure [Line Items]
Cash Dividends Paid to Parent, Consolidated Subsidiaries	$ 3.7	$ 3.7
Statutory Accounting Practices, Statutory Capital and Surplus, Balance	23.7
Statutory Accounting Practices, Statutory Capital and Surplus Required	10.3
Stock Repurchase Program, Number of Shares Authorized to be Repurchased			100
Extraordinary Dividends [Member]
Shareholders' Equity Disclosure [Line Items]
Cash Dividends Paid to Parent, Consolidated Subsidiaries	$ 1.1	$ 1.1

Shareholders' Equity Share Repu

Shareholders' Equity Share Repurchases (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Stockholders' Equity [Abstract]
Common shares repurchases, shares	19,000,000	9,000,000
Common share repurchases, average price per share	$ 236.72	$ 173.54
Common share repurchases	$ 4,500	$ 1,500	$ 1,280
Board authorized shares remaining	94,000,000	42,000,000

Share-Based Compensation (Narra

Share-Based Compensation (Narrative) (Details) - USD ($) shares in Millions, $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	42
Deferred Compensation, Recorded Liability	$ 988	$ 865
Employee Stock Purchase Plan (ESPP) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	7

Share-Based Compensation (Stock

Share-Based Compensation (Stock Option and SAR Activity) (Details) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding at the beginning of the period | shares	37
Granted | shares	7
Exercised | shares	(8)
Forfeitures | shares	(1)
Outstanding at the end of the period | shares	35
Exercisable at end of period | shares	16
Vested and expected to vest, end of period | shares	34
Outstanding at beginning of period, Weighted-Average Exercise Price | $ / shares	$ 102
Granted, Weighted-Average Exercise Price | $ / shares	229
Exercised, Weighted-Average Exercise Price | $ / shares	78
Forfeitures, Weighted Average Exercise Price | $ / shares	162
Outstanding at end of period, Weighted-Average Exercise Price | $ / shares	131
Exercisable at end of period, Weighted-Average Exercise Price | $ / shares	87
Vested and expected to vest end of period, Weighted-Average Exercise Price | $ / shares	$ 129
Outstanding at end of period, Weighted Average Remaining Contractual Term (in years)	6 years 6 months
Exercisable at end of period, Weighted Average Remaining Contractual Term (in years)	5 years
Vested and expected to vest end of period, Weighted Average Remaining Contractual Term (in years)	6 years 6 months
Outstanding at end of period, Aggregate Intrinsic Value | $	$ 4,114
Exercisable at end of period, Aggregate Intrinsic Value | $	2,560
Vested and expected to vest end of period, Aggregate Intrinsic Value | $	$ 4,072

Share-Based Compensation (Restr

Share-Based Compensation (Restricted Share Activity) (Details) - Restricted Stock [Member] shares in Millions	12 Months Ended
	Dec. 31, 2018$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Nonvested at beginning of period | shares	7
Granted | shares	2
Vested | shares	(3)
Nonvested at end of period | shares	6
Nonvested at beginning of period, Weighted-Average Grant Date Fair Value per Share | $ / shares	$ 128
Weighted-average grant date fair value per share | $ / shares	229
Vested, Weighted Average Grant Date Fair Value per share | $ / shares	119
Nonvested at end of period, Weighted-Average Grant Date Fair Value per Share | $ / shares	$ 163

Share-Based Compensation Other

Share-Based Compensation Other Share-Based Compensation Data (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense, before tax	$ 638	$ 597	$ 485
Share-based compensation expense, net of tax effects	587	531	417
Income tax benefit realized from share-based award exercises	239	$ 431	$ 236
Unrecognized compensation expense related to share awards	$ 628
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	1 year 3 months 18 days
Stock Options and SARs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average grant date fair value of shares granted, per share	$ 43	$ 29	$ 20
Total intrinsic value of stock options and SARs exercised	$ 1,431	$ 1,473	$ 595
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average grant date fair value per share	$ 229	$ 163	$ 115
Total fair value of restricted shares vested	$ 521	$ 460	$ 274
Employee Stock Purchase Plan (ESPP) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares purchased	2	2	2

Share-Based Compensation (Share

Share-Based Compensation (Share-Based Compensation Principal Fair Value Assumptions) (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield			1.80%
Forfeiture rate	5.00%	5.00%	5.00%
Expected Life in years	5 years 7 months 9 days	5 years 8 months 12 days
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	2.60%	1.90%	1.20%
Expected Volatility	18.70%	18.50%	20.80%
Expected dividend yield	1.30%	1.40%
Expected Life in years			5 years 7 months 9 days
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	3.10%	2.10%	1.40%
Expected Volatility	19.30%	20.70%	22.50%
Expected dividend yield	1.50%	1.60%
Expected Life in years			5 years 10 months 29 days

Commitments and Contingencies_3

Commitments and Contingencies (Narrative) (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Loss Contingencies [Line Items]
Operating Leases, Rent Expense		$ 751	$ 710	$ 608
Undrawn Letters Of Credit		83
Surety Bonds Outstanding		$ 1,300
Payments to be made to Acquire Businesses, Gross	$ 4,300

Commitments and Contingencies F

Commitments and Contingencies Future Lease Payments (Details) $ in Millions	Dec. 31, 2018USD ($)
Operating Leased Assets [Line Items]
2,019	$ 669
2,020	592
2,021	511
2,022	423
2,023	338
Thereafter	$ 1,343

Segment Financial Information_3

Segment Financial Information (Narrative) (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement [Line Items]
Number of Reportable Segments	4
UNITED STATES
Statement [Line Items]
Disclosure on Geographic Areas Percentage of Revenue from External Customers	96.00%	96.00%	97.00%
Disclosure on Geographic Areas Percentage of Long Lived Assets	76.00%	77.00%
Revenues [Member] | CMS [Member]
Statement [Line Items]
Concentration Risk, Percentage	30.00%	28.00%	25.00%

Segment Financial Information_4

Segment Financial Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement [Line Items]
Premiums, revenues - unaffiliated customers	$ 178,087	$ 158,453	$ 144,118
Products, revenues - unaffiliated customers	29,601	26,366	26,658
Services, revenues - unaffiliated customers	17,183	15,317	13,236
Investment and other income	1,376	1,023	828
Total revenues	226,247	201,159	184,840
Earnings from operations	17,344	15,209	12,930
Interest expense	(1,400)	(1,186)	(1,067)
Earnings before income taxes	15,944	14,023	11,863
Total assets	152,221	139,058	122,810
Purchases of property, equipment and capitalized software	2,063	2,023	1,705
Depreciation and amortization	2,428	2,245	2,055
Optum
Statement [Line Items]
Investment and other income	548	365	217
Total revenues	101,280	91,185	83,593
Earnings from operations	8,231	6,711	5,623
Interest expense	0	0	0
Earnings before income taxes	8,231	6,711	5,623
Total assets	74,788	67,755	56,739
Purchases of property, equipment and capitalized software	1,302	1,286	1,065
Depreciation and amortization	1,583	1,487	1,331
Unaffiliated Customers
Statement [Line Items]
Premiums, revenues - unaffiliated customers	178,087	158,453	144,118
Products, revenues - unaffiliated customers	29,601	26,366	26,658
Services, revenues - unaffiliated customers	17,183	15,317	13,236
Total revenues	224,871	200,136	184,012
Unaffiliated Customers | Optum
Statement [Line Items]
Premiums, revenues - unaffiliated customers	3,805	3,744	3,663
Products, revenues - unaffiliated customers	29,601	26,366	26,657
Services, revenues - unaffiliated customers	8,817	7,427	5,722
Total revenues	42,223	37,537	36,042
Affiliated Customers
Statement [Line Items]
Total revenues	0	0	0
Affiliated Customers | Optum
Statement [Line Items]
Total revenues	58,509	53,283	47,334
Operating Segments | UnitedHealthcare
Statement [Line Items]
Investment and other income	828	658	611
Total revenues	183,476	163,257	148,581
Earnings from operations	9,113	8,498	7,307
Interest expense	0	0	0
Earnings before income taxes	9,113	8,498	7,307
Total assets	82,938	76,676	70,505
Purchases of property, equipment and capitalized software	761	737	640
Depreciation and amortization	845	758	724
Operating Segments | OptumHealth
Statement [Line Items]
Investment and other income	481	340	208
Total revenues	24,145	20,570	16,908
Earnings from operations	2,430	1,823	1,428
Interest expense	0	0	0
Earnings before income taxes	2,430	1,823	1,428
Total assets	29,837	26,931	18,656
Purchases of property, equipment and capitalized software	593	510	345
Depreciation and amortization	439	380	297
Operating Segments | OptumInsight
Statement [Line Items]
Investment and other income	21	5	1
Total revenues	9,008	8,087	7,333
Earnings from operations	2,243	1,770	1,513
Interest expense	0	0	0
Earnings before income taxes	2,243	1,770	1,513
Total assets	11,039	11,273	9,017
Purchases of property, equipment and capitalized software	517	588	571
Depreciation and amortization	654	614	559
Operating Segments | OptumRx
Statement [Line Items]
Investment and other income	46	20	8
Total revenues	69,536	63,755	60,440
Earnings from operations	3,558	3,118	2,682
Interest expense	0	0	0
Earnings before income taxes	3,558	3,118	2,682
Total assets	33,912	29,551	29,066
Purchases of property, equipment and capitalized software	192	188	149
Depreciation and amortization	490	493	475
Operating Segments | Unaffiliated Customers | UnitedHealthcare
Statement [Line Items]
Premiums, revenues - unaffiliated customers	174,282	154,709	140,455
Products, revenues - unaffiliated customers	0	0	1
Services, revenues - unaffiliated customers	8,366	7,890	7,514
Total revenues	182,648	162,599	147,970
Operating Segments | Unaffiliated Customers | OptumHealth
Statement [Line Items]
Premiums, revenues - unaffiliated customers	3,805	3,744	3,663
Products, revenues - unaffiliated customers	52	44	48
Services, revenues - unaffiliated customers	4,925	4,013	2,498
Total revenues	8,782	7,801	6,209
Operating Segments | Unaffiliated Customers | OptumInsight
Statement [Line Items]
Premiums, revenues - unaffiliated customers	0	0	0
Products, revenues - unaffiliated customers	111	106	103
Services, revenues - unaffiliated customers	3,280	2,849	2,670
Total revenues	3,391	2,955	2,773
Operating Segments | Unaffiliated Customers | OptumRx
Statement [Line Items]
Premiums, revenues - unaffiliated customers	0	0	0
Products, revenues - unaffiliated customers	29,438	26,216	26,506
Services, revenues - unaffiliated customers	612	565	554
Total revenues	30,050	26,781	27,060
Operating Segments | Affiliated Customers | UnitedHealthcare
Statement [Line Items]
Total revenues	0	0	0
Operating Segments | Affiliated Customers | OptumHealth
Statement [Line Items]
Total revenues	14,882	12,429	10,491
Operating Segments | Affiliated Customers | OptumInsight
Statement [Line Items]
Total revenues	5,596	5,127	4,559
Operating Segments | Affiliated Customers | OptumRx
Statement [Line Items]
Total revenues	39,440	36,954	33,372
Optum Eliminations
Statement [Line Items]
Investment and other income	0	0	0
Total revenues	(1,409)	(1,227)	(1,088)
Earnings from operations	0	0	0
Interest expense	0	0	0
Earnings before income taxes	0	0	0
Total assets	0	0	0
Purchases of property, equipment and capitalized software	0	0	0
Depreciation and amortization	0	0	0
Optum Eliminations | Unaffiliated Customers
Statement [Line Items]
Premiums, revenues - unaffiliated customers	0	0	0
Products, revenues - unaffiliated customers	0	0	0
Services, revenues - unaffiliated customers	0	0	0
Total revenues	0	0	0
Optum Eliminations | Affiliated Customers
Statement [Line Items]
Total revenues	(1,409)	(1,227)	(1,088)
Corporate and Eliminations
Statement [Line Items]
Investment and other income	0	0	0
Total revenues	(58,509)	(53,283)	(47,334)
Earnings from operations	0	0	0
Interest expense	(1,400)	(1,186)	(1,067)
Earnings before income taxes	(1,400)	(1,186)	(1,067)
Total assets	(5,505)	(5,373)	(4,434)
Purchases of property, equipment and capitalized software	0	0	0
Depreciation and amortization	0	0	0
Corporate and Eliminations | Unaffiliated Customers
Statement [Line Items]
Premiums, revenues - unaffiliated customers	0	0	0
Products, revenues - unaffiliated customers	0	0	0
Services, revenues - unaffiliated customers	0	0	0
Total revenues	0	0	0
Corporate and Eliminations | Affiliated Customers
Statement [Line Items]
Total revenues	$ (58,509)	$ (53,283)	$ (47,334)

Quarterly Financial Data (Una_3

Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues									$ 226,247	$ 201,159	$ 184,840
Operating costs									208,903	185,950	171,910
Earnings from operations									17,344	15,209	12,930
Net earnings									12,382	10,823	7,073
Net earnings attributable to UnitedHealth Group common shareholders									$ 11,986	$ 10,558	$ 7,017
Net earnings per share attributable to UnitedHealth Group common stockholders:
Basic									$ 12.45	$ 10.95	$ 7.37
Diluted									$ 12.19	$ 10.72	$ 7.25
Quarterly Financial Data (Unaudited) [Member]
Revenues	$ 58,417	$ 56,556	$ 56,086	$ 55,188	$ 52,061	$ 50,322	$ 50,053	$ 48,723
Operating costs	53,920	51,966	51,882	51,135	48,084	46,234	46,322	45,310
Earnings from operations	4,497	4,590	4,204	4,053	3,977	4,088	3,731	3,413
Net earnings	3,164	3,284	3,010	2,924	3,721	2,561	2,350	2,191
Net earnings attributable to UnitedHealth Group common shareholders	$ 3,040	$ 3,188	$ 2,922	$ 2,836	$ 3,617	$ 2,485	$ 2,284	$ 2,172
Net earnings per share attributable to UnitedHealth Group common stockholders:
Basic	$ 3.16	$ 3.31	$ 3.04	$ 2.94	$ 3.73	$ 2.57	$ 2.37	$ 2.28
Diluted	$ 3.10	$ 3.24	$ 2.98	$ 2.87	$ 3.65	$ 2.51	$ 2.32	$ 2.23

Schedule I (Details)

Schedule I (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Condensed Financial Statements, Captions [Line Items]
Cash Dividends Paid to Parent, Consolidated Subsidiaries	$ 3,700	$ 3,700
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Cash Dividends Paid to Parent, Consolidated Subsidiaries	5,600	3,400	$ 3,700
Return of capital to parent company	4,196	3,375	$ 2,143
Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Other Long-term Debt	$ 1,300	$ 625

Schedule I Condensed Balance Sh

Schedule I Condensed Balance Sheets (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 10,866	$ 11,981	$ 10,430	$ 10,923
Total current assets	38,692	37,084
Other assets	4,326	3,575
Total assets	152,221	139,058	122,810
Current liabilities:
Accounts payable and accrued liabilities	16,705	15,180
Commercial paper and current maturities of long-term debt	1,973	2,857
Total current liabilities	53,209	50,463
Long-term debt, less current maturities	34,581	28,835
Other liabilities	5,730	5,556
Total liabilities	95,994	87,036
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; 960 and 969 issued and outstanding	10	10
Additional paid-in capital	0	1,703
Retained earnings	55,846	48,730
Accumulated other comprehensive loss	(4,160)	(2,667)
Total liabilities and shareholders’ equity	152,221	139,058
Parent Company [Member]
Current assets:
Cash and cash equivalents	434	359	$ 180	$ 29
Other current assets	197	575
Total current assets	631	934
Equity in net assets of subsidiaries	83,244	76,231
Long-term notes receivable from subsidiaries	4,461	4,278
Other assets	972	839
Total assets	89,308	82,282
Current liabilities:
Accounts payable and accrued liabilities	618	502
Current portion of notes payable to subsidiaries	714	466
Commercial paper and current maturities of long-term debt	1,744	2,749
Total current liabilities	3,076	3,717
Long-term debt, less current maturities	33,490	28,318
Long-term notes payable to subsidiaries	560	1,518
Other liabilities	486	953
Total liabilities	37,612	34,506
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; 960 and 969 issued and outstanding	10	10
Additional paid-in capital	0	1,703
Retained earnings	55,846	48,730
Accumulated other comprehensive loss	(4,160)	(2,667)
Total UnitedHealth Group shareholders’ equity	51,696	47,776
Total liabilities and shareholders’ equity	$ 89,308	$ 82,282

Schedule I Balance Sheet Docume

Schedule I Balance Sheet Document (Details) - $ / shares shares in Millions	Dec. 31, 2018	Dec. 31, 2017
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	3,000	3,000
Common stock, shares issued	960	969
Common Stock, shares outstanding	960	969
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	10	10
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Parent Company [Member]
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	3,000	3,000
Common stock, shares issued	960	969
Common Stock, shares outstanding	960	969
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	10	10
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0

Schedule I Condensed Statement

Schedule I Condensed Statement of Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues:
Investment and other income	$ 1,376	$ 1,023	$ 828
Total revenues	226,247	201,159	184,840
Operating costs:
Interest expense	1,400	1,186	1,067
Total operating costs	208,903	185,950	171,910
Loss before income taxes	15,944	14,023	11,863
Benefit for income taxes	3,562	3,200	4,790
Net earnings	11,986	10,558	7,017
Other comprehensive (loss) income	(1,517)	14	653
Comprehensive income	10,469	10,572	7,670
Parent Company [Member]
Revenues:
Investment and other income	194	527	522
Total revenues	194	527	522
Operating costs:
Operating costs	35	0	(22)
Interest expense	1,285	1,114	995
Total operating costs	1,320	1,114	973
Loss before income taxes	(1,126)	(587)	(451)
Benefit for income taxes	251	214	165
Loss of parent company	(875)	(373)	(286)
Equity in undistributed income of subsidiaries	12,861	10,931	7,303
Net earnings	11,986	10,558	7,017
Other comprehensive (loss) income	(1,517)	14	653
Comprehensive income	$ 10,469	$ 10,572	$ 7,670

Schedule I Statement of Cash Fl

Schedule I Statement of Cash Flows (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating activities
Cash flows from operating activities	$ 15,713	$ 13,596	$ 9,795
Investing activities
Cash paid for acquisitions	(5,997)	(2,131)	(1,760)
Other, net	226	126	(37)
Cash flows (used for) from investing activities	(12,385)	(8,599)	(9,355)
Financing activities
Common stock repurchases	(4,500)	(1,500)	(1,280)
Proceeds from common stock issuances	838	688	429
Repayments of commercial paper, net	(201)	(3,508)	(382)
Proceeds from issuance of long-term debt	6,935	5,291	3,968
Repayments of long-term debt	(2,600)	(4,398)	(2,596)
Other, net	(1,386)	(413)	(581)
Cash flows used for financing activities	(4,365)	(3,441)	(1,011)
Increase in cash and cash equivalents	(1,115)	1,551	(493)
Cash and cash equivalents, beginning of period	11,981	10,430	10,923
Cash and cash equivalents, end of period	10,866	11,981	10,430
Supplemental cash flow disclosures
Cash paid for interest	1,410	1,133	1,055
Cash paid for income taxes	3,257	4,004	4,726
Supplemental schedule of non-cash investing activities
Common stock issued for acquisitions	0	2,164	0
Parent Company [Member]
Operating activities
Cash flows from operating activities	6,099	2,021	4,294
Investing activities
Issuances of notes to subsidiaries	(1,420)	0	(824)
Repayments of notes to subsidiaries	1,419	2,071	0
Cash paid for acquisitions	(4,066)	(2,313)	(2,292)
Return of capital to parent company	4,196	3,375	2,143
Capital contributions to subsidiaries	(1,259)	(959)	(765)
Other, net	4	0	168
Cash flows (used for) from investing activities	(1,126)	2,174	(1,570)
Financing activities
Common stock repurchases	(4,500)	(1,500)	(1,280)
Proceeds from common stock issuances	838	688	429
Cash dividends paid	(3,320)	(2,773)	(2,261)
Repayments of commercial paper, net	(201)	(3,508)	(382)
Proceeds from issuance of long-term debt	6,935	5,291	3,968
Repayments of long-term debt	(2,600)	(3,472)	(2,596)
(Repayments) proceeds of notes from subsidiary	(1,127)	1,704	(30)
Other, net	(923)	(446)	(421)
Cash flows used for financing activities	(4,898)	(4,016)	(2,573)
Increase in cash and cash equivalents	75	179	151
Cash and cash equivalents, beginning of period	359	180	29
Cash and cash equivalents, end of period	434	359	180
Supplemental cash flow disclosures
Cash paid for interest	1,294	1,062	974
Cash paid for income taxes	2,379	3,455	4,557
Supplemental schedule of non-cash investing activities
Common stock issued for acquisitions	0	2,164	0
Conversion of note receivable from subsidiaries to equity	$ 0	$ 4,378	$ 0

Schedule I Maturities of Commer

Schedule I Maturities of Commercial Paper and Long-Term Debt (Details) $ in Millions	Dec. 31, 2018USD ($)
Debt Instrument [Line Items]
2,019	$ 1,973
2,020	3,350
2,021	3,350
2,022	3,215
2,023	2,325
Thereafter	22,775
Parent Company [Member]
Debt Instrument [Line Items]
2,019	1,750
2,020	3,150
2,021	3,150
2,022	3,015
2,023	2,125
Thereafter	$ 22,477