CONSOLIDATED STATEMENT OF SHAREHOLDERS' EQUITY (DEFICIT) (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement of Stockholders' Equity [Abstract]
Dividends declared per share attributable to Moody's common shareholders (in USD per share)	$ 2.48	$ 2.24	$ 2.00
Currency translation adjustment, tax	$ (65)	$ 78	$ 9
Net actuarial gains (losses) and prior service cost, tax	18	(10)	(8)
Amortization of actuarial losses and prior service costs included in net income, tax	$ 5	2	$ 1
Net unrealized and unrealized gain (loss) on cash flow hedges, tax		$ 16