Assets Measured at Fair Value on Nonrecurring Basis (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
Jun. 30, 2012	Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Reduction in fair value of loans based on the fair value of the underlying collateral as allowed by ASC 310	$ 7	$ 32

Reduction in fair value of loans measured on nonrecurring basis based on the fair value of the underlying collateral with an offset to the allowance for credit losses.

No definition available.

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