Commitments, Contingencies and Guarantees - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) attorney_general
Loss Contingencies [Line Items]
Contractual obligation	$ 2,000
Other liabilities reserve	$ 2
Loss emergence period	1 year
Washington and Pennsylvania
Loss Contingencies [Line Items]
Number of state attorneys general | attorney_general	3