INCOME TAXES - Narrative (Details) - USD ($) $ in Thousands		1 Months Ended	12 Months Ended
	Aug. 10, 2020	Apr. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Line Items]
Income tax receivable			$ 200	$ 2,000
Uncertain tax benefits accrued			2,700	2,700	$ 2,700	$ 2,700
Valuation allowance			100	400
Net change in total valuation allowance			300	300
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense			200	300	100
Interest and penalties accrued related to uncertain income tax positions			600	400
CARES Act Deferral Of Employer Share Social Security Tax			55,400
Other long-term obligations			33,622	5,905
Payroll and employee benefits			146,929	120,877
Funding Received From CARES Act		$ 100,000
Provider relief fund advance			60,000	0
Income Tax Expense (Benefit)			$ 25,635	$ 42,503	$ 38,859
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period			622,829
Social Security Tax [Member]
Income Tax Disclosure [Line Items]
Other long-term obligations			$ 27,700
Payroll and employee benefits			27,700
Executive Stock Option Exercise [Member]
Income Tax Disclosure [Line Items]
Recognized share-based compensation tax benefit			92,100
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	500,000
COVID-19 Deferral of Social Security Taxes [Member]
Income Tax Disclosure [Line Items]
CARES Act Deferral Of Employer Share Social Security Tax			55,000
Other long-term obligations			28,000
Payroll and employee benefits			$ 28,000
Minimum [Member]
Income Tax Disclosure [Line Items]
Tax years open to examination			2007
Maximum [Member]
Income Tax Disclosure [Line Items]
Tax years open to examination			2020
State Tax Credit [Member]
Income Tax Disclosure [Line Items]
Tax credits			$ 3,700
Federal [Member] | Executive Stock Option Exercise [Member]
Income Tax Disclosure [Line Items]
Recognized share-based compensation tax benefit			19,400
State and Local Jurisdiction [Member] | Executive Stock Option Exercise [Member]
Income Tax Disclosure [Line Items]
Recognized share-based compensation tax benefit			4,600
State and Local Jurisdiction [Member] | Net Operating Loss [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards			$ 47,500