Preferred stock - Summary of Preferred Dividends Paid (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2022	Jun. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Class of Stock [Line Items]
Preferred dividends paid	$ 69	$ 34	$ 66	$ 177	$ 166
Series A Preferred Stock
Class of Stock [Line Items]
Depositary shares per share	1.00%			1.00%
Dividend paid per share (usd per share)	$ 1,011.11	$ 1,022.22	$ 1,011.11	$ 3,044.44	$ 3,033.33
Preferred dividends paid	$ 5	$ 5	$ 5	$ 15	$ 15
Series D Preferred Stock
Class of Stock [Line Items]
Depositary shares per share	1.00%			1.00%
Dividend paid per share (usd per share)		$ 2,250		$ 2,250	$ 2,250
Preferred dividends paid	$ 0	$ 11	$ 0	$ 11	$ 11
Series E Preferred Stock
Class of Stock [Line Items]
Depositary shares per share	1.00%			1.00%
Dividend paid per share (usd per share)			$ 898.50		$ 2,735
Preferred dividends paid			$ 10		$ 28
Series F Preferred Stock
Class of Stock [Line Items]
Depositary shares per share	1.00%			1.00%
Dividend paid per share (usd per share)	$ 2,312.5		$ 2,312.5	$ 4,625	$ 4,625
Preferred dividends paid	$ 23	0	$ 23	$ 46	$ 46
Series G Preferred Stock
Class of Stock [Line Items]
Depositary shares per share	1.00%			1.00%
Dividend paid per share (usd per share)	$ 2,350		$ 2,350	$ 4,700	$ 4,700
Preferred dividends paid	$ 23	$ 0	$ 23	$ 47	$ 47
Series H Preferred Stock
Class of Stock [Line Items]
Depositary shares per share	1.00%			1.00%
Dividend paid per share (usd per share)	$ 925.00	$ 925.00	$ 925.00	$ 2,775	$ 3,258.06
Preferred dividends paid	$ 6	$ 6	$ 5	$ 17	$ 19
Series I Preferred Stock
Class of Stock [Line Items]
Depositary shares per share	1.00%			1.00%
Dividend paid per share (usd per share)	$ 937.50	$ 937.50		$ 3,145.83
Preferred dividends paid	$ 12	$ 12		$ 41