CONSOLIDATED STATEMENT OF SHAREHOLDERS' EQUITY (DEFICIT) (Parenthetical) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Stockholders' Equity [Abstract]
Dividends declared per share attributable to Moody's common shareholders (in USD per share)	$ 2.00	$ 1.76	$ 1.14
Currency translation adjustment, tax	$ 9	$ 7	$ 23
Net actuarial losses and prior service costs, tax	8	(2)	(8)
Amortization of actuarial losses and prior service costs included in net income, tax	$ 1	1	3
Net unrealized and unrealized gain on cash flow hedges, tax		$ 1	$ 1

Aggregate dividends declared during the period for each share of common stock outstanding.

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Amount of tax expense (benefit) for (increase) decrease in value of benefit obligation for change in actuarial assumptions and increase (decrease) in value of plan assets from experience different from that assumed of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit.

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Amount, after reclassification, of tax expense (benefit) for gain (loss) from derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness.

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Amount of tax expense (benefit), after reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature.

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