Computation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Basic and diluted:
Net Income	$ 225,035	$ 145,362	$ 190,388	$ 210,527	$ 178,738	$ 157,265	$ 195,449	$ 215,719	$ 771,312	$ 747,171	$ 750,698
Less: Net income attributable to noncontrolling interest	$ (5,426)	$ (4,117)	$ (4,994)	$ (4,472)	$ (4,530)	$ (5,400)	$ (9,872)	$ (24,960)	(19,009)	(44,762)	(70,170)
Less: Net income attributable to unvested restricted share grants									(362)	(314)	(281)
Net income attributable to UHS—basic and diluted									$ 751,941	$ 702,095	$ 680,247
Weighted average number of common shares—basic									95,652	97,208	98,797
Total basic earnings per share	$ 2.32	$ 1.48	$ 1.93	$ 2.13	$ 1.80	$ 1.56	$ 1.91	$ 1.95	$ 7.86	$ 7.22	$ 6.89
Weighted average number of common shares—basic									95,652	97,208	98,797
Net effect of dilutive stock options and grants based on the treasury stock method									673	1,172	1,897
Weighted average number of common shares and equivalents?diluted									96,325	98,380	100,694
Total diluted earnings per share	$ 2.31	$ 1.47	$ 1.91	$ 2.12	$ 1.78	$ 1.54	$ 1.89	$ 1.93	$ 7.81	$ 7.14	$ 6.76