Risk Management and Derivatives - Additional Information (Detail) - USD ($)	3 Months Ended
	Aug. 31, 2016	Aug. 31, 2015	May 31, 2016
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Equity	$ 189,000,000	$ 190,000,000
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	$ 302,000,000
Maximum term over which the Company is hedging exposures to the variability of cash flows for its forecasted and recorded transactions (in months)	27 months
Gain (loss) on fair value hedge ineffectiveness, net	$ 0	0
Amount o ineffectiveness on net investment hedges	0	0
Derivative instruments in a net liability position	$ 96,000,000
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
Derivatives designated as cash flow hedges
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Total notional amount of outstanding derivatives	$ 11,300,000,000
Cash and Cash Equivalents
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Collateral posted on derivative liabilities	31,000,000
Embedded derivatives
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Total notional amount of outstanding derivatives	294,000,000
Interest rate swaps | Derivatives designated as fair value hedges
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Total notional amount of outstanding derivatives	0
Interest rate swaps | Cash and Cash Equivalents
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Collateral posted on derivative liabilities	8,000,000		$ 0
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
Foreign exchange forwards and options | Cash and Cash Equivalents
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Collateral posted on derivative liabilities	23,000,000		$ 0
Undesignated derivative instruments
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Total notional amount of outstanding derivatives	7,700,000,000
Derivatives formally designated as hedging instruments | Interest rate swaps | Derivatives designated as cash flow hedges
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Total notional amount of outstanding derivatives	1,500,000,000.0
Cash Flow Hedges
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Equity	$ 180,000,000	187,000,000
Cash Flow Hedges | Revisions
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Equity		$ 40,000,000