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Share-Based Compensation - Assumption (Details) - Parent Issuer UHS - Options - $ / shares
6 Months Ended
Jun. 30, 2017
Jun. 30, 2016
Assumptions used in determining the fair value of stock options granted under the Black-Scholes model    
Risk-free interest rate (as a percent) 1.62% 1.50%
Expected volatility (as a percent) 29.00% 30.90%
Expected option life 4 years 7 months 13 days 5 years 9 months 29 days
Black-Scholes Value of options (in dollars per share) $ 0.32 $ 0.33