Dispositions and Acquisitions - Additional Information (Detail)	3 Months Ended
Mar. 31, 2018 USD ($) Bed	Mar. 31, 2017 USD ($)
Business Acquisition [Line Items]
Acquisition, cash paid	$ 21,000,000	$ 18,000,000
Aggregate cash proceeds from divestiture of businesses	$ 0	$ 0
Gulfport Behavioral Health System
Business Acquisition [Line Items]
Number of beds \| Bed	109

Number of beds available in acquired hospital in business acquisition.

No definition available.

Name:	uhs_NumberOfBedsAvailableInAcquiredHospitalInBusinessAcquisition
Namespace Prefix:	uhs_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_BusinessAcquisitionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3213-108585

+ Details

Name:	us-gaap_PaymentsToAcquireBusinessesGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

This element represents the cash inflow during the period from the sale of a component of the entity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3179-108585

+ Details

Name:	us-gaap_ProceedsFromDivestitureOfBusinessesNetOfCashDivested
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_BusinessAcquisitionAxis=uhs_GulfportBehavioralHealthSystemMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: