CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement of Comprehensive Income [Abstract]
Net Income	$ 487	$ 374
Foreign Currency Adjustments:
Foreign currency translation adjustment - Pre Tax	(175)	(27)
Foreign currency translation adjustments - Tax	5	0
Foreign currency translation adjustments - Net of Tax	(170)	(27)
Net gains on net investment hedges - Pre Tax	119	30
Net gains on net investment hedges, Tax	(30)	(7)
Net gains on net investment hedges, Net of Tax	89	23
Cash Flow Hedges:
Net realized and unrealized (losses) gains on cash flow hedges - Pre Tax	(48)	0
Net realized and unrealized (losses) gains on cash flow hedges - Tax	12	0
Net realized and unrealized (losses) gains on cash flow hedges - Net of Tax	(36)	0
Reclassification of losses (gains) included in net income - Pre Tax	1	0
Reclassification of losses (gains) included in net income - Tax	0	0
Reclassification of losses (gains) included in net income - Net of Tax	1	0
Pension and Other Retirement Benefits:
Amortization of actuarial losses and prior service costs included in net income - Pre Tax	2	1
Amortization of actuarial losses and prior service costs included in net income - Tax	(1)	(1)
Amortization of actuarial losses and prior service costs included in net income - Net of Tax	1	0
Net actuarial (losses) gains and prior service costs - Pre Tax	(1)	1
Net actuarial (losses) gains and prior service costs - Tax	0	0
Net actuarial (losses) gains and prior service costs - Net of Tax	(1)	1
Total other comprehensive income (loss) - Pre Tax	(102)	5
Total other comprehensive income (loss) - Tax	(14)	(8)
Total other comprehensive income (loss) - Net of Tax	(116)	(3)
Comprehensive income	371	371
Less: comprehensive income (loss) attributable to noncontrolling interests	(2)	8
Comprehensive Income Attributable to Moody's	$ 373	$ 363