CONDENSED CONSOLIDATED STATEMENT OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Total Radnet, Inc.'s Equity	Noncontrolling Interests
Beginning balance (in shares) at Dec. 31, 2017		47,723,915
Beginning balance, value at Dec. 31, 2017	$ 69,925	$ 5	$ 212,261	$ (548)	$ (150,158)	$ 61,560	$ 8,365
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation (in shares)		0
Stock-based compensation	3,643		3,643			3,643
Issuance of restricted stock and other awards (in shares)		512,701
Sale of noncontrolling interests, net of taxes	45,895		18,663			18,663	27,232
Distributions paid to noncontrolling interests	(759)						(759)
Change in cumulative foreign currency translation adjustment	22			22		22
Change in fair value of cash flow hedge, net of taxes	3,095			3,095		3,095
Net loss	(5,454)				(7,338)	(7,338)	1,884
Ending balance (in shares) at Mar. 31, 2018		48,236,616
Ending balance, value at Mar. 31, 2018	116,367	$ 5	234,567	2,569	(157,496)	79,645	36,722
Beginning balance (in shares) at Dec. 31, 2017		47,723,915
Beginning balance, value at Dec. 31, 2017	69,925	$ 5	212,261	(548)	(150,158)	61,560	8,365
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Change in fair value of cash flow hedge, net of taxes	2,876
Ending balance (in shares) at Dec. 31, 2018		48,977,485
Ending balance, value at Dec. 31, 2018	200,253	$ 5	242,835	2,259	(117,915)	127,184	73,069
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of options (in shares)		10,000
Issuance of common stock upon exercise of options	50		50			50
Stock-based compensation (in shares)		586,000
Stock-based compensation	4,514		4,514			4,514
Issuance of restricted stock and other awards (in shares)		67,786
Issuance of common stock for purchase of membership interest (in shares)		440,207
Issuance of common stock for purchase of membership interest in HVRA	6,000		6,000			6,000
Sale of noncontrolling interests, net of taxes	5,097		3,089			3,089	2,008
Contribution from noncontrolling partner	750						750
Change in cumulative foreign currency translation adjustment	(8)			(8)		(8)
Change in fair value of cash flow hedge, net of taxes	(1,196)			(1,196)		(1,196)
Net loss	(1,922)				(3,733)	(3,733)	1,811
Ending balance (in shares) at Mar. 31, 2019		50,081,478
Ending balance, value at Mar. 31, 2019	$ 213,538	$ 5	$ 256,488	$ 1,055	$ (121,648)	$ 135,900	$ 77,638