Employee Retirement Benefits - Defined contribution plan (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jan. 31, 2014 contribution_plan	Jan. 31, 2013	Jan. 31, 2012
Schedule of Defined Contribution Plans Disclosure [Line Items]
Number of defined contribution plans	2
Current payroll matching percentage by the Company	4.00%
Participant contribution rate for company stock, maximum	20.00%
Total contribution expense	$ 2,412	$ 2,021	$ 1,556
Vista Research [Member]
Schedule of Defined Contribution Plans Disclosure [Line Items]
Current payroll matching percentage by the Company	3.00%