Other comprehensive income (loss) - Components (Details) - USD ($) $ in Millions		3 Months Ended			9 Months Ended
		Sep. 30, 2021	Jun. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Pre-tax amount
Total other comprehensive income (loss), Pre-tax amount		$ (334)	$ 165	$ 583	$ (1,198)	$ 1,676
Tax (expense) benefit
Total other comprehensive income (loss), Tax (expense) benefit		1	(16)	3	180	(392)
After-tax amount
Total other comprehensive (loss) income, net of tax	[1]	(333)	149	586	(1,018)	1,284
Foreign currency translation
Pre-tax amount
Other comprehensive income (loss), Pre-tax amount		(158)	38	262	(247)	101
Total other comprehensive income (loss), Pre-tax amount		(158)	38	262	(247)	101
Tax (expense) benefit
Other comprehensive income (loss), Tax (expense) benefit		(44)	13	69	(54)	(24)
Total other comprehensive income (loss), Tax (expense) benefit		(44)	13	69	(54)	(24)
After-tax amount
Other comprehensive income (loss), After-tax amount		(202)	51	331	(301)	77
Total other comprehensive (loss) income, net of tax		(202)	51	331	(301)	77
Unrealized gain (loss) on assets available-for-sale
Pre-tax amount
Other comprehensive income (loss), Pre-tax amount		(201)	106	297	(1,021)	1,529
Reclassification adjustment, Pre-tax amount		(2)	(2)	(9)	(4)	(27)
Total other comprehensive income (loss), Pre-tax amount		(203)	104	288	(1,025)	1,502
Tax (expense) benefit
Other comprehensive income (loss), Tax (expense) benefit		51	(29)	(64)	245	(360)
Reclassification adjustment, Tax (expense) benefit		0	1	3	1	7
Total other comprehensive income (loss), Tax (expense) benefit		51	(28)	(61)	246	(353)
After-tax amount
Other comprehensive income (loss), After-tax amount		(150)	77	233	(776)	1,169
Reclassification adjustment, After-tax amount		(2)	(1)	(6)	(3)	(20)
Total other comprehensive (loss) income, net of tax		(152)	76	227	(779)	1,149
Defined benefit plans
Pre-tax amount
Reclassification adjustment, Pre-tax amount		28	27	24	83	72
Total other comprehensive income (loss), Pre-tax amount		28	27	24	83	72
Tax (expense) benefit
Reclassification adjustment, Tax (expense) benefit		(6)	(2)	(4)	(14)	(15)
Total other comprehensive income (loss), Tax (expense) benefit		(6)	(2)	(4)	(14)	(15)
After-tax amount
Reclassification adjustment, After-tax amount		22	25	20	69	57
Total other comprehensive (loss) income, net of tax		22	25	20	69	57
Unrealized gain (loss) on cash flow hedges
Pre-tax amount
Other comprehensive income (loss), Pre-tax amount		1	0	9	2	(1)
Reclassification adjustment, Pre-tax amount		(2)	(4)	0	(11)	2
Total other comprehensive income (loss), Pre-tax amount		(1)	(4)	9	(9)	1
Tax (expense) benefit
Other comprehensive income (loss), Tax (expense) benefit		0	0	(1)	0	1
Reclassification adjustment, Tax (expense) benefit		0	1	0	2	(1)
Total other comprehensive income (loss), Tax (expense) benefit		0	1	(1)	2	0
After-tax amount
Other comprehensive income (loss), After-tax amount		1	0	8	2	0
Reclassification adjustment, After-tax amount		(2)	(3)	0	(9)	1
Total other comprehensive (loss) income, net of tax		(1)	(3)	8	(7)	1
Unrealized gain (loss) on cash flow hedges | Staff expense
Pre-tax amount
Reclassification adjustment, Pre-tax amount		(2)	(4)	0	(11)	2
Tax (expense) benefit
Reclassification adjustment, Tax (expense) benefit		0	1	0	2	(1)
After-tax amount
Reclassification adjustment, After-tax amount		$ (2)	$ (3)	$ 0	$ (9)	$ 1

[1] Other comprehensive (loss) income attributable to The Bank of New York Mellon Corporation shareholders was $(333) million for the quarter ended Sept. 30, 2021, $149 million for the quarter ended June 30, 2021, $584 million for the quarter ended Sept. 30, 2020, $(1,018) million for the nine months ended Sept. 30, 2021 and $1,284 million for the nine months ended Sept. 30, 2020.