Realized Gross Gains, Realized Gross Losses and Recognized Gross Impairments on Securities (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011
Gain (Loss) on Investments [Line Items]
Realized gross gains	$ 62	$ 91	$ 19
Realized gross losses		(34)	(9)
Recognized gross impairments	(22)	(60)	(5)
Net securities gains (losses)	$ 40	$ (3)	$ 5

This item represents the total realized gain (loss) included in earnings for the period as a result of selling marketable securities categorized as available-for-sale or held-to-maturity. Additionally, this item would include any losses recognized for other than temporary impairments of the subject investments in debt and equity securities.

No definition available.

Name:	bk_NetSecuritiesGainLoss
Namespace Prefix:	bk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration