Preferred stock Preferred Stock Summary (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013
Class of Stock [Line Items]
Total shares issued and outstanding (shares)	15,826		15,826
Carrying value	$ 1,562	[1]	$ 1,562	[1]
Series A Preferred Stock
Class of Stock [Line Items]
Per annum dividend rate	Greater of (i) three-month LIBOR plus 0.565% for the related distribution period; or (ii) 4.000%
Per annum dividend rate (percent)	4.00%
Liquidation preference per share (usd per share)	$ 100,000
Total shares issued and outstanding (shares)	5,001		5,001
Carrying value	500	[1]	500	[1]
Dividends Payable, Date Declared	Jan. 17, 2014	[2],[3]	Oct. 16, 2013	[2],[3]	Jul. 17, 2013	[2],[3]	Apr. 09, 2013	[2],[3]	Jan. 16, 2013	[2],[3]
Dividends Payable, Date of Record	Mar. 05, 2014	[2],[3]	Dec. 05, 2013	[2],[3]	Sep. 05, 2013	[2],[3]	Jun. 05, 2013	[2],[3]	Mar. 05, 2013	[2],[3]
Dividend payment, day and month	Mar. 20, 2014	[2],[3]	Dec. 20, 2013	[2],[3]	Sep. 20, 2013	[2],[3]	Jun. 20, 2013	[2],[3]	Mar. 20, 2013	[2],[3]
Depository share, value of preferred stock (percent)	1.00%
Dividend paid per share (usd per share)	$ 10.0000	[2],[3]	$ 10.1111	[2],[3]	$ 10.2222	[2],[3]	$ 10.2222	[2],[3]	$ 10.0000	[2],[3]
Series C Noncumulative Perpetual Preferred Stock
Class of Stock [Line Items]
Per annum dividend rate (percent)	5.20%
Preferred Stock Redemption Period Following Regulatory Capital Treatment Event	90 days
Liquidation preference per share (usd per share)	$ 100,000
Total shares issued and outstanding (shares)	5,825		5,825
Carrying value	568	[1]	568	[1]
Dividends Payable, Date Declared	Jan. 17, 2014	[2],[4]	Oct. 16, 2013	[2],[4]	Jul. 17, 2013	[2],[4]	Apr. 09, 2013	[2],[4]	Jan. 16, 2013	[2],[4]
Dividends Payable, Date of Record	Mar. 05, 2014	[2],[4]	Dec. 05, 2013	[2],[4]	Sep. 05, 2013	[2],[4]	Jun. 05, 2013	[2],[4]	Mar. 05, 2013	[2],[4]
Dividend payment, day and month	Mar. 20, 2014	[2],[4]	Dec. 20, 2013	[2],[4]	Sep. 20, 2013	[2],[4]	Jun. 20, 2013	[2],[4]	Mar. 20, 2013	[2],[4]
Depository share, value of preferred stock (percent)	0.025%
Dividend paid per share (usd per share)	$ 0.3250	[2],[4]	$ 0.3250	[2],[4]	$ 0.3250	[2],[4]	$ 0.3250	[2],[4]	$ 0.3250	[2],[4]
Series D Preferred Stock
Class of Stock [Line Items]
Per annum dividend rate	4.50% commencing Dec. 20, 2013 to but excluding June 20, 2023, then a floating rate equal to the three-month LIBOR plus 2.46%
Per annum dividend rate (percent)	4.50%
Preferred Stock Redemption Period Following Regulatory Capital Treatment Event	90 days
Liquidation preference per share (usd per share)	$ 100,000
Total shares issued and outstanding (shares)	5,000		5,000
Carrying value	$ 494	[1]	$ 494	[1]
Dividends Payable, Date Declared			Oct. 16, 2013	[2],[5]
Dividends Payable, Date of Record			Dec. 05, 2013	[2],[5]
Dividend payment, day and month			Dec. 20, 2013	[2],[5]
Depository share, value of preferred stock (percent)	1.00%
Dividend paid per share (usd per share)			$ 26.6250	[2],[5]
LIBOR | Series A Preferred Stock
Class of Stock [Line Items]
Preferred stock, basis spread on variable rate (percent)	0.565%
LIBOR | Series D Preferred Stock
Class of Stock [Line Items]
Preferred stock, basis spread on variable rate (percent)	2.46%

[1] The carrying value of the Series C and Series D preferred stock is recorded net of issuance costs.

[2] Dividends are noncumulative

[3] Dividend per Normal Preferred Capital Security of Mellon Capital IV, each representing 1/100th interest in a share of Series A preferred stock.

[4] Dividend per depositary share, each representing a 1/4,000th interest in a share of Series C preferred stock.

[5] Dividend per depository share, each representing a 1/100th interest in a share of Series D preferred stock.