Cover Page - shares	9 Months Ended
	Sep. 30, 2020	Nov. 02, 2020
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Amendment Flag	false
Document Period End Date	Sep. 30, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Entity Registrant Name	MEDNAX, INC.
Entity Central Index Key	0000893949
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Common Stock, Shares Outstanding		85,598,299
Title of 12(b) Security	Common Stock
Trading Symbol	MD
Security Exchange Name	NYSE
Entity File Number	001-12111
Entity Incorporation, State or Country Code	FL
Entity Tax Identification Number	26-3667538
Entity Address, Address Line One	1301 Concord Terrace
Entity Address, City or Town	Sunrise
Entity Address, State or Province	FL
Entity Address, Postal Zip Code	33323
City Area Code	954
Local Phone Number	384-0175
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false