Income Taxes (Details) (USD $) In Thousands, unless otherwise specified				12 Months Ended
	Jan. 31, 2012	Jan. 31, 2011	Jan. 31, 2010	Jan. 31, 2012 UNITED STATES	Jan. 31, 2012 CANADA
Income Tax Contingency [Line Items]
Pre-tax book income, domestic				$ 74,219
Pre-tax book income, foreign					1,338
Total unrecognized tax benefits that, if recognized, would affect the company's effective tax rate	2,318	2,023	1,727
Accrued interest and penalties related to unrecognized tax benefits	$ 1,379	$ 1,112	$ 857