Derivative Instruments - Asset and Liability Management Derivative Positions of Company (Parenthetical) (Detail) - Asset and Liability Management Positions [Member] - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Notional Value, Assets	$ 36,566	$ 27,953
Notional Value, Liabilities	39,889	31,679
Fair Value, Liabilities	172	125
Swap [Member] | Visa Class B Shares [Member]
Derivative [Line Items]
Notional Value, Liabilities	1,500	1,500
Fair Value, Liabilities	$ 74	$ 84
Derivative Liability Average Remaining Maturity Period	1 year 3 months	1 year 6 months
Underwriting Purchase and Sale Commitments [Member]
Derivative [Line Items]
Notional Value, Assets	$ 210	$ 1
Notional Value, Liabilities	$ 210	$ 1