EMPLOYEE BENEFIT PLANS - USPI Management Equity Plan (Details) - USD ($) $ in Millions	1 Months Ended		12 Months Ended
	Feb. 29, 2020	Feb. 24, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Stock-based compensation costs, pretax			$ 44	$ 42	$ 46
USPI Management Equity Plan
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Granted (in shares)			2,025,000
USPI Management Equity Plan | Equity Option
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Stock-based compensation costs, pretax			$ 12
2015 USPI Management Equity Plan | Nonqualified Plan
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Vesting period, days to be exercised before termination			90 days
2015 USPI Management Equity Plan | Nonqualified Plan | Equity Option
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Expected payment for vested securities and termination of plan		$ 35
2015 USPI Management Equity Plan | Nonqualified Plan | Equity Option | Share-based Payment Arrangement, Tranche One
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Vesting percentage			50.00%
2015 USPI Management Equity Plan | Nonqualified Plan | Equity Option | Share-based Payment Arrangement, Tranche Two
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Vesting percentage			50.00%
2015 USPI Management Equity Plan | Nonqualified Plan | Equity Option | Minimum
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Percent of common stock allocated to plan			10.00%
Vesting period			3 years
2015 USPI Management Equity Plan | Nonqualified Plan | Equity Option | Maximum
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Vesting period			4 years
2020 USPI Management Equity Plan | Restricted Stock
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Granted (in shares)			2,556,353
Restricted stock (in shares)			2,025,056
Vested and expected to vest at the end of the period (in shares)			382,550
2020 USPI Management Equity Plan | Restricted Stock | Share-based Payment Arrangement, Tranche One
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Vesting period	3 years
Vesting percentage	20.00%
2020 USPI Management Equity Plan | Restricted Stock | Share-based Payment Arrangement, Tranche Two
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Vesting percentage	40.00%
2020 USPI Management Equity Plan | Nonqualified Plan | Equity Option
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Stock-based compensation costs, pretax			$ 12	$ 11	$ 18