Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Aug. 31, 2014
Income Tax Contingency [Line Items]
Deferred tax assets	$ 48
Federal net operating loss and tax credit carryforwards	33
State net operating loss carryforwards	8
Differences between financial and tax reporting	$ 7
Minimum [Member] | Federal [Member]
Income Tax Contingency [Line Items]
Federal net operating loss and tax credit carryforwards life expectancy, maximum	16 years
Minimum [Member] | State [Member]
Income Tax Contingency [Line Items]
Federal net operating loss and tax credit carryforwards life expectancy, maximum	5 years
Maximum [Member] | Federal [Member]
Income Tax Contingency [Line Items]
Federal net operating loss and tax credit carryforwards life expectancy, maximum	20 years
Maximum [Member] | State [Member]
Income Tax Contingency [Line Items]
Federal net operating loss and tax credit carryforwards life expectancy, maximum	20 years