Cash and Cash Equivalents - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Jan. 31, 2014
Cash and Cash Equivalents [Line Items]
Original maturity date	Three months or less
Minimum percentage of cash and cash equivalents invested in U.S. Treasury obligations and repurchase agreements	80.00%
Joint Venture [Member]
Cash and Cash Equivalents [Line Items]
Cash held with consolidated joint venture	$ 117.7