Risk Management and Derivatives - Additional Information (Detail) - USD ($)	3 Months Ended
	Aug. 31, 2015	May. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Percentage of anticipated exposures hedged (percent)	100.00%
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	$ 603,000,000
Maximum term over which the Company is hedging exposures to the variability of cash flows for its forecasted and recorded transactions (in months)	33 months
Aggregate fair value of derivative instruments in net liability position	$ 0
Collateral received from counterparties to hedging instruments	468,000,000	$ 968,000,000
Embedded derivatives
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Total notional amount of outstanding derivatives	225,000,000
Undesignated Derivative Instruments
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Total notional amount of outstanding derivatives	$ 5,300,000,000
Minimum
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Typical time period that anticipated exposures are hedged against (in months)	12 months
Minimum fair value of outstanding derivative above which the credit related contingent features require the derivative party to post collateral	$ 50,000,000
Maximum
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Typical time period that anticipated exposures are hedged against (in months)	24 months
Fair Value Hedging | Interest rate swap
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Total notional amount of outstanding derivatives	$ 100,000,000
Cash Flow Hedging
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Total notional amount of outstanding derivatives	13,500,000,000
Cash Flow Hedging | Designated as Hedging Instrument | Interest rate swap
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Total notional amount of outstanding derivatives	1,000,000,000
Net Investment Hedging [Member] | Foreign exchange forwards and options
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Derivative assets (liabilities), at fair value, net	0
Securities Pledged as Collateral | Foreign exchange forwards and options
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Collateral received from counterparties to hedging instruments		74,000,000
Accrued Liabilities
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Collateral received from counterparties to hedging instruments	0
Cash and Cash Equivalents
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Collateral received from counterparties to hedging instruments	468,000,000
Cash and Cash Equivalents | Interest rate swap
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Collateral received from counterparties to hedging instruments	51,000,000	68,000,000
Cash and Cash Equivalents | Foreign exchange forwards and options
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Collateral received from counterparties to hedging instruments	$ 417,000,000	$ 900,000,000