Credit Concentrations - Additional Information (Detail) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Concentration Risk [Line Items]
Cash deposits held at central banks	$ 56,600	$ 90,470
GS Bank USA [Member]
Concentration Risk [Line Items]
Cash deposits held at the Federal Reserve Bank of New York	26,930	29,200
Other Assets at Amortized Cost [Member]
Concentration Risk [Line Items]
Amount of US government obligations classified as held to maturity	$ 5,060	$ 498