Credit Concentrations - Credit Concentration, Government and Federal Agency Obligations (Detail) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
U.S. Government And Federal Agency Obligations Held By The Firm [Member]
Concentration Risk [Line Items]
Concentration risk, Credit risk, Financial instrument, Maximum exposure	$ 64,492	$ 63,844
Concentration risk, Credit risk, Financial instrument, Maximum exposure, As a percentage of total Assets	7.30%	7.40%
Non-U.S. Government and Agency Obligations Held By The Firm [Member]
Concentration Risk [Line Items]
Concentration risk, Credit risk, Financial instrument, Maximum exposure	$ 38,036	$ 31,772
Concentration risk, Credit risk, Financial instrument, Maximum exposure, As a percentage of total Assets	4.30%	3.70%