Risk Management and Derivatives - Additional Information (Detail) - USD ($)	3 Months Ended
	Aug. 31, 2018	May 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Deferred net gains (net of tax) on both outstanding and matured derivatives accumulated in other comprehensive income are expected to be reclassified to net income during the next twelve months as a result of underlying hedged transactions also being recorded in net income	$ 92,000,000
Maximum term over which the Company is hedging exposures to the variability of cash flows for its forecasted and recorded transactions (in months)	21 months
Aggregate fair value of derivative instruments in net liability position	$ 0
Collateral received on derivative assets	31,000,000	$ 23,000,000
Minimum
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Minimum fair value of outstanding derivative above which the credit related contingent features require the derivative party to post collateral	$ 50,000,000
Derivatives designated as cash flow hedges
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Additional period for forecasted transaction expected to occur	2 months
Percentage of anticipated exposures hedged (percent)	100.00%
Total notional amount of outstanding derivatives	$ 9,900,000,000
Derivatives designated as cash flow hedges | Minimum
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Typical time period that anticipated exposures are hedged against (in months)	12 months
Derivatives designated as cash flow hedges | Maximum
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Typical time period that anticipated exposures are hedged against (in months)	24 months
Embedded derivatives
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Total notional amount of outstanding derivatives	$ 315,000,000
Interest rate swaps | Derivatives designated as fair value hedges
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Total notional amount of outstanding derivatives	0
Foreign exchange forwards and options | Cash and Cash Equivalents
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Collateral received on derivative assets	31,000,000	$ 23,000,000
Foreign exchange forwards and options | Derivatives designated as net investment hedges
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Derivative assets (liabilities), at fair value, net	0
Undesignated derivative instruments
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Total notional amount of outstanding derivatives	$ 6,900,000,000