Cash and Cash Equivalents - Additional Information (Detail) (Joint Venture [Member], USD $)	9 Months Ended
	Oct. 31, 2014	Jan. 31, 2014
Joint Venture [Member]
Cash and Cash Equivalents [Line Items]
Cash held with consolidated joint venture	$ 209,900,000	$ 117,700,000
Distributions to joint venture partner	$ 0