SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details - Narrative)								1 Months Ended			6 Months Ended	12 Months Ended			24 Months Ended
	Nov. 05, 2019 USD ($)	Aug. 01, 2019 USD ($)	Jan. 01, 2019 USD ($)	Apr. 12, 2018 USD ($)	Mar. 01, 2018 USD ($)	Feb. 01, 2018 USD ($) shares	Mar. 24, 2017 USD ($)	Aug. 31, 2020 USD ($)	Sep. 30, 2019 USD ($)	Nov. 06, 2014 USD ($)	Dec. 31, 2020 USD ($) joint_venture numberOfAgreement shares	Dec. 31, 2020 USD ($) joint_venture numberOfAgreement shares	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Oct. 31, 2025 USD ($)	Oct. 01, 2020 USD ($)	Oct. 11, 2019 shares	Jul. 31, 2019	Jun. 30, 2019 USD ($) numberOfAgreement	Feb. 28, 2019 USD ($)	Apr. 01, 2017	Nov. 30, 2006 USD ($)
Property, Plant and Equipment [Line Items]
Provider relief funding												$ 26,264,000	$ 0	$ 0
Deferred social security taxes											$ 16,300,000	16,300,000
Factored accounts receivable												29,500,000
Factoring receivable											20,500,000	20,500,000
Service fee revenue												1,071,840,000	1,154,179,000	975,146,000
Deferred revenue liability											1,200,000	1,200,000
Deferred financing costs, net of accumulated amortization											1,800,000	1,800,000	1,600,000
Goodwill											472,879,000	472,879,000	441,973,000	418,093,000
Indefinite lived intangible assets											7,100,000	7,100,000	11,300,000			$ 4,200,000
Loss on impairment												4,170,000	0	3,937,000
Workers' compensation liability, current											4,100,000	4,100,000	3,800,000
Medical malpractice deductible per incidence											10,000	$ 10,000	10,000
Employer matching contribution, percent												1.00%
Employee contribution, percent												4.00%
Expected employee contribution												$ 0	2,900,000
Contract loss accrual														4,600,000
Contract loss accrual, written off														558,000
Amount of loss recognized in income on derivative (current period ineffective portion)											24,400,000
Monthly amortization of deferred hedge gains											400,000
Total net assets											$ 61,644,000	$ 61,644,000	60,375,000
Number of unconsolidated joint ventures | joint_venture											13	13
Payments to acquire additional interest in subsidiaries												$ 1,635,000	103,000	2,000,000
Loss on equity method investment													134,000
Management service fees												11,300,000	11,400,000	13,800,000
Forecast
Property, Plant and Equipment [Line Items]
Monthly amortization of deferred hedge gains															$ 300,000
C O V I D19 Pandemic
Property, Plant and Equipment [Line Items]
Advance medicare payments												43,200,000
Advance insurance carrier payments												$ 5,000,000.0
Medic Vision
Property, Plant and Equipment [Line Items]
Equity interest percentage							12.50%				14.21%	14.21%
Investment at cost					$ 200,000		$ 1,000,000.0
Option to purchase additional equity method investment							$ 1,400,000
Ownership interest percentage acquired					1.96%
Initial ownership percentage after dilution					12.25%
Total net assets											$ 1,200,000	$ 1,200,000
Turner Imaging Systems
Property, Plant and Equipment [Line Items]
Investment at cost						$ 2,000,000.0
Shares purchased (in shares) | shares						2,100,000
Turner Imaging
Property, Plant and Equipment [Line Items]
Preferred stock issued upon conversion (in shares) | shares																	80,000
WhiteRabbit.ai Inc.
Property, Plant and Equipment [Line Items]
Investment at cost	$ 1,000,000.0
Payments to fund loan to related parties	$ 2,500,000
Santa Monica Imaging Group
Property, Plant and Equipment [Line Items]
Payments to acquire additional interest in subsidiaries								$ 1,600,000
Santa Monica Imaging Group | RadNet
Property, Plant and Equipment [Line Items]
Equity interest percentage			35.00%																		40.00%
Loss on equity method investment			$ 2,000
Santa Monica Imaging Group | Cedars Sinai Medical Center
Property, Plant and Equipment [Line Items]
Equity interest percentage																					60.00%
Additional equity interest acquired			5.00%
Investment owned, at fair value			$ 134,000
2016 Caps | LIBOR
Property, Plant and Equipment [Line Items]
Basis spread on variable rate											2.00%	2.00%
September 2020
Property, Plant and Equipment [Line Items]
Notional amounts											$ 150,000,000	$ 150,000,000
October 2020
Property, Plant and Equipment [Line Items]
Notional amounts											350,000,000	350,000,000
Radiologix
Property, Plant and Equipment [Line Items]
Contract loss accrual																						$ 8,900,000
Hudson Valley Radiology Associates
Property, Plant and Equipment [Line Items]
Goodwill																				$ 3,100,000
Hudson Valley Radiology Associates | Primedex Health Systems Inc. and Radiologix
Property, Plant and Equipment [Line Items]
Unfavorable lease contracts acquired, gross																				4,000,000.0
Unfavorable lease contracts acquired																				$ 2,800,000
Garden State Radiology Network LLC
Property, Plant and Equipment [Line Items]
Goodwill		$ 2,000,000.0
Equity interest percentage		51.00%																49.00%
Investment at cost										$ 2,200,000
Loss on equity method investment		$ (1,300,000)
Nulogix, Inc.
Property, Plant and Equipment [Line Items]
Goodwill		$ 1,300,000
Equity interest percentage		75.00%		25.00%														25.00%
Investment at cost		$ 1,500,000		$ 2,000,000.0
Loss on equity method investment		$ 500,000
Health Insurance
Property, Plant and Equipment [Line Items]
Self-insurance accrual											6,600,000	$ 6,600,000	4,900,000
Minimum
Property, Plant and Equipment [Line Items]
Share-based payment award, award vesting period												3 years
Share-based payment award, expiration period												5 years
Minimum | Blue Shield
Property, Plant and Equipment [Line Items]
Stop loss policy claim amount											250,000	$ 250,000
Minimum | Dignity Health | Glendale Advanced Imaging | Joint Venture
Property, Plant and Equipment [Line Items]
Economic interest												35.00%
Minimum | Propery and equipment, net
Property, Plant and Equipment [Line Items]
PP&E useful life												3 years
Minimum | Leasehold improvements
Property, Plant and Equipment [Line Items]
PP&E useful life												3 years
Maximum
Property, Plant and Equipment [Line Items]
Share-based payment award, award vesting period												5 years
Share-based payment award, expiration period												10 years
Maximum | Blue Shield
Property, Plant and Equipment [Line Items]
Stop loss policy claim amount											1,000,000.0	$ 1,000,000.0
Maximum | Dignity Health | Glendale Advanced Imaging | Joint Venture
Property, Plant and Equipment [Line Items]
Economic interest												55.00%
Maximum | Propery and equipment, net
Property, Plant and Equipment [Line Items]
PP&E useful life												15 years
Maximum | Leasehold improvements
Property, Plant and Equipment [Line Items]
PP&E useful life												15 years
Paycheck Protection Program Loans | C O V I D19 Pandemic
Property, Plant and Equipment [Line Items]
Face Value											4,000,000.0	$ 4,000,000.0
Barclays
Property, Plant and Equipment [Line Items]
Total credit facilities outstanding											0	0	0
SunTrust
Property, Plant and Equipment [Line Items]
Total credit facilities outstanding											$ 0	0	0
Imaging On Call
Property, Plant and Equipment [Line Items]
Loss on impairment														3,900,000
Goodwill impairment														3,800,000
Write off of the reporting unit trade name														100,000
Net service fee revenue | eRAD
Property, Plant and Equipment [Line Items]
Service fee revenue												$ 8,600,000	$ 10,100,000	$ 6,800,000
Restated Plan
Property, Plant and Equipment [Line Items]
Shares authorized (in shares) | shares											14,000,000	14,000,000
Restated Plan | Minimum
Property, Plant and Equipment [Line Items]
Share-based payment award, award vesting period												3 years
Share-based payment award, expiration period												5 years
Restated Plan | Maximum
Property, Plant and Equipment [Line Items]
Share-based payment award, award vesting period												5 years
Share-based payment award, expiration period												10 years
US Attorneys Office For The Western District of New York
Property, Plant and Equipment [Line Items]
Loss contingency accrual liability																			$ 2,300,000
Settled Litigation | US Attorneys Office For The Western District of New York
Property, Plant and Equipment [Line Items]
Litigation settlement									$ 2,200,000
2016 Caps
Property, Plant and Equipment [Line Items]
Number of forward interest rate cap agreements | numberOfAgreement											2	2
Interest rate caps premium liability											$ 5,300,000	$ 5,300,000
2019 SWAPS
Property, Plant and Equipment [Line Items]
Number of forward interest rate cap agreements | numberOfAgreement																			4,000
Notional amounts																			$ 500,000,000
2019 SWAPS | 2019 SWAPS - Interest Rate Contracts
Property, Plant and Equipment [Line Items]
Notional amounts																			$ 100,000,000
2019 SWAPS | 2019 SWAPS - Interest Rate Contracts | LIBOR
Property, Plant and Equipment [Line Items]
Basis spread on variable rate																			1.96%
2019 SWAPS | October 2023
Property, Plant and Equipment [Line Items]
Notional amounts																			$ 50,000,000
2019 SWAPS | October 2025
Property, Plant and Equipment [Line Items]
Notional amounts																			200,000,000
2019 SWAPS1 | 2019 SWAPS - Interest Rate Contracts
Property, Plant and Equipment [Line Items]
Notional amounts																			$ 400,000,000
2019 SWAPS1 | 2019 SWAPS - Interest Rate Contracts | LIBOR
Property, Plant and Equipment [Line Items]
Basis spread on variable rate																			2.05%
Promissory note | Turner Imaging
Property, Plant and Equipment [Line Items]
Convertible promissory note			$ 143,000