Income Taxes (Detail) (USD $)	3 Months Ended		9 Months Ended
	Oct. 31, 2013	Oct. 31, 2012	Oct. 31, 2013	Oct. 31, 2012	Jan. 31, 2013
Income Tax Contingency [Line Items]
Income tax (benefit)/expense	$ (3,940,000)	$ (1,202,000)	$ 52,091,000	$ 5,625,000
Discrete period tax (benefit) expense related to valuation allowance recorded on domestic deferred tax assets	(3,300,000)		47,300,000
Tax benefit resulting from a change in the Company's decision to carryback its domestic net operating loss generated in the prior fiscal year	4,300,000
Effective tax rate for continued operations	20.20%	(16.10%)	(77.20%)	35.30%
Unrecognized tax benefits	16,000,000		16,000,000		13,400,000
Unrecognized tax benefits that would affect the effective tax rate if recognized	16,000,000		16,000,000		13,400,000
Decrease in unrecognized tax benefits due to settlements of audit issues and expiration of statutes of limitation			6,800,000
Liability for income tax-related interest and penalties	9,500,000		9,500,000		8,800,000
Investment In Diberil [Member]
Income Tax Contingency [Line Items]
Income tax (benefit)/expense				0
Domestic Tax Authority [Member]
Income Tax Contingency [Line Items]
Expected cumulative loss position period	3 years		3 years
Foreign Tax Authority [Member]
Income Tax Contingency [Line Items]
Deferred tax asset	2,300,000		2,300,000
Foreign Tax Contingencies [Member]
Income Tax Contingency [Line Items]
Tax expense on unrecognized tax benefits resulted from certain foreign tax contingencies			$ 3,600,000	$ 200,000