RELATED-PARTY TRANSACTIONS (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Selling, general and administrative expenses	$ 459,628,000	$ 345,884,000	$ 338,456,000
Sale of management notes receivable	1,310,000	0	0
Sale Of Notes Receivable
Related Party Transaction [Line Items]
Sale of management notes receivable	1,300,000
Madison Dearborn Partners VI-B, L.P. | Option Care Acquisition [Member]
Related Party Transaction [Line Items]
Due to joint ventures	300,000
Walgreen Co. | Option Care Acquisition [Member]
Related Party Transaction [Line Items]
Due to joint ventures	300,000
HC Group Holdings I, LLC | Loans Funded For Membership Unit Purchase
Related Party Transaction [Line Items]
Amount credited to paid-in capital for membership units sold and funded	0	400,000	0
Shareholder redemptions	2,400,000	0	100,000
Cash distributions	2,000,000
Notes redeemed	400,000
Management
Related Party Transaction [Line Items]
Selling, general and administrative expenses	1,500,000	2,000,000	2,000,000
Notes receivable	0	1,600,000
Management | Sale Of Notes Receivable
Related Party Transaction [Line Items]
Sale of management notes receivable	1,100,000
Accrued interest expense	200,000
Joint Venture
Related Party Transaction [Line Items]
Due to joint ventures	4,300,000	900,000
Management fee income	$ 2,500,000	2,200,000	$ 1,300,000
Due from joint ventures		$ 100,000