Netting Arrangements for Certain Financial Instruments and Securities Financing Activities - Additional Information (Detail) $ in Billions	Mar. 31, 2019 USD ($)
Derivative [Line Items]
Notional amount of derivative	$ 458.5
Over the Counter Trades [Member]
Derivative [Line Items]
Notional amount of derivative	240.0
Exchange Cleared [Member]
Derivative [Line Items]
Notional amount of derivative	202.8
Exchange Traded [Member]
Derivative [Line Items]
Notional amount of derivative	$ 15.7