Risk Management and Derivatives - Additional Information (Detail) - USD ($)	12 Months Ended
	May. 31, 2015	May. 31, 2014
Derivative Instruments and Hedging Activities Disclosures [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	$ 685,000,000
Maximum term over which the Company is hedging exposures to the variability of cash flows for its forecasted and recorded transactions (in months)	36 months
Aggregate fair value of derivative instruments in net liability position	$ 4,000,000
Collateral received from counterparties to hedging instruments	968,000,000	$ 0
Not designated as derivative instrument
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total notional amount of outstanding derivatives	4,400,000,000
Embedded derivatives
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total notional amount of outstanding derivatives	$ 205,000,000
Minimum
Derivative Instruments and Hedging Activities Disclosures [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 Disclosures [Line Items]
Typical time period that anticipated exposures are hedged against (in months)	24 months
Derivatives designated as cash flow hedges
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total notional amount of outstanding derivatives	$ 14,400,000,000
Derivatives designated as cash flow hedges | Designated as Hedging Instrument | Interest rate swaps
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total notional amount of outstanding derivatives	1,000,000,000
Derivatives designated as fair value hedges | Interest rate swaps
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total notional amount of outstanding derivatives	100,000,000
Derivatives designated as net investment hedges | Foreign Exchange Contract [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative Assets (Liabilities), at Fair Value, Net	0
Cash and Cash Equivalents
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Collateral received from counterparties to hedging instruments	968,000,000
Cash and Cash Equivalents | Interest rate swaps
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Collateral received from counterparties to hedging instruments	68,000,000
Cash and Cash Equivalents | Foreign Exchange Contract [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Collateral received from counterparties to hedging instruments	900,000,000	$ 0
Securities pledged as collateral
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Collateral received from counterparties to hedging instruments	74,000,000
Securities pledged as collateral | Interest rate swaps
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Collateral received from counterparties to hedging instruments	$ 74,000,000