Document and Entity Information shares in Millions	9 Months Ended
	Sep. 30, 2017 shares
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	Q3
Trading Symbol	MCO
Entity Registrant Name	MOODYS CORP /DE/
Entity Central Index Key	0001059556
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding	191.1