Document and Entity Information shares in Millions	3 Months Ended
	Mar. 31, 2019 shares
Document Documentand Entity Information [Abstract]
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Registrant Name	MOODYS CORP /DE/
Document Type	10-Q
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Fiscal Year Focus	2019
Trading Symbol	MCO
Document Period End Date	Mar. 31, 2019
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Central Index Key	0001059556
Entity Common Stock Shares Outstanding	189.6