Credit Facility - Additional Information (Detail) (USD $)	0 Months Ended	3 Months Ended	12 Months Ended
	Dec. 07, 2011	Jan. 31, 2015	Jan. 31, 2015	Dec. 07, 2011
Wells Credit Facility [Member]
Line of Credit Facility [Line Items]
Revolving credit facility term	5 years
Maximum borrowing capacity	$ 100,000,000			$ 100,000,000
Revolving credit facility interest rate description			Borrowings under the Wells Credit Facility bear interest at a floating rate which, at the Company’s option, may be determined by reference to a LIBOR Rate or a Base Rate, plus 1.75% or 0.75%, respectively, (as defined in the Wells Credit Facility, 1.92% as of January 31, 2015)
Revolving credit facility reference to floating interest rate			1.92%
New credit facility maturity date				Dec. 07, 2016
Direct borrowings		0	0
Letters of credit outstanding		7,000,000	7,000,000
Proceeds from debt borrowed		15,000,000
Wells Credit Facility [Member] | Minimum [Member]
Line of Credit Facility [Line Items]
Availability under Wells Fargo Facility		29,000,000	29,000,000
Wells Credit Facility [Member] | LIBOR [Member]
Line of Credit Facility [Line Items]
Revolving credit facility reference to floating interest rate			1.75%
Wells Credit Facility [Member] | Base Rate [Member]
Line of Credit Facility [Line Items]
Revolving credit facility reference to floating interest rate			0.75%
Swing-line loans [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity		$ 12,500,000.0	$ 12,500,000.0