Other comprehensive income (loss) - Components (Details) - USD ($) $ in Millions		3 Months Ended			9 Months Ended
		Sep. 30, 2020	Jun. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Pre-tax amount
Total other comprehensive income (loss), Pre-tax amount		$ 583	$ 1,114	$ (121)	$ 1,676	$ 656
Tax (expense) benefit
Total other comprehensive income (loss), Tax (expense) benefit		3	(230)	(87)	(392)	(289)
After-tax amount
Total other comprehensive income (loss), net of tax	[1]	586	884	(208)	1,284	367
Foreign currency translation
Pre-tax amount
Other comprehensive income (loss), Pre-tax amount		262	104	(213)	101	(157)
Total other comprehensive income (loss), Pre-tax amount		262	104	(213)	101	(157)
Tax (expense) benefit
Other comprehensive income (loss), Tax (expense) benefit		69	11	(63)	(24)	(80)
Total other comprehensive income (loss), Tax (expense) benefit		69	11	(63)	(24)	(80)
After-tax amount
Other comprehensive income (loss), After-tax amount		331	115	(276)	77	(237)
Total other comprehensive income (loss), net of tax		331	115	(276)	77	(237)
Unrealized gain (loss) on assets available-for-sale
Pre-tax amount
Other comprehensive income (loss), Pre-tax amount		297	989	88	1,529	794
Reclassification adjustment, Pre-tax amount		(9)	(9)	1	(27)	(7)
Total other comprehensive income (loss), Pre-tax amount		288	980	89	1,502	787
Tax (expense) benefit
Other comprehensive income (loss), Tax (expense) benefit		(64)	(236)	(25)	(360)	(205)
Reclassification adjustment, Tax (expense) benefit		3	2	0	7	2
Total other comprehensive income (loss), Tax (expense) benefit		(61)	(234)	(25)	(353)	(203)
After-tax amount
Other comprehensive income (loss), After-tax amount		233	753	63	1,169	589
Reclassification adjustment, After-tax amount		(6)	(7)	1	(20)	(5)
Total other comprehensive income (loss), net of tax		227	746	64	1,149	584
Defined benefit plans
Pre-tax amount
Other comprehensive income (loss), Pre-tax amount					0	(11)
Reclassification adjustment, Pre-tax amount		24	24	13	72	38
Total other comprehensive income (loss), Pre-tax amount		24	24	13	72	27
Tax (expense) benefit
Other comprehensive income (loss), Tax (expense) benefit					0	2
Reclassification adjustment, Tax (expense) benefit		(4)	(5)	(3)	(15)	(8)
Total other comprehensive income (loss), Tax (expense) benefit		(4)	(5)	(3)	(15)	(6)
After-tax amount
Other comprehensive income (loss), After-tax amount					0	(9)
Reclassification adjustment, After-tax amount		20	19	10	57	30
Total other comprehensive income (loss), net of tax		20	19	10	57	21
Unrealized gain (loss) on cash flow hedges
Pre-tax amount
Other comprehensive income (loss), Pre-tax amount		9	3	(9)	(1)	(1)
Reclassification adjustment, Pre-tax amount		0	3	(1)	2	0
Total other comprehensive income (loss), Pre-tax amount		9	6	(10)	1	(1)
Tax (expense) benefit
Other comprehensive income (loss), Tax (expense) benefit		(1)	(1)	4	1	(2)
Reclassification adjustment, Tax (expense) benefit		0	(1)	0	(1)	2
Total other comprehensive income (loss), Tax (expense) benefit		(1)	(2)	4	0	0
After-tax amount
Other comprehensive income (loss), After-tax amount		8	2	(5)	0	(3)
Reclassification adjustment, After-tax amount		0	2	(1)	1	2
Total other comprehensive income (loss), net of tax		8	4	(6)	1	(1)
Unrealized gain (loss) on cash flow hedges | Interest expense
Pre-tax amount
Reclassification adjustment, Pre-tax amount		0	0	1	0	1
Tax (expense) benefit
Reclassification adjustment, Tax (expense) benefit		0	0	0	0	0
After-tax amount
Reclassification adjustment, After-tax amount		0	0	1	0	1
Unrealized gain (loss) on cash flow hedges | Staff expense
Pre-tax amount
Reclassification adjustment, Pre-tax amount		0	3	(2)	2	(1)
Tax (expense) benefit
Reclassification adjustment, Tax (expense) benefit		0	(1)	0	(1)	2
After-tax amount
Reclassification adjustment, After-tax amount		$ 0	$ 2	$ (2)	$ 1	$ 1

[1] Other comprehensive income (loss) attributable to The Bank of New York Mellon Corporation shareholders was $584 million for the quarter ended Sept. 30, 2020, $884 million for the quarter ended June 30, 2020, $(205) million for the quarter ended Sept. 30, 2019, $1,284 million for the nine months ended Sept. 30, 2020 and $368 million for the nine months ended Sept. 30, 2019.