Fair Value Measurements (Details 1) (Fair Value, Measurements, Recurring [Member], USD $) In Thousands, unless otherwise specified	Jan. 31, 2013
Level 1 [Member]
Assets:
Short-term investments	$ 84,918
Prepaid expenses and other	0
Other long-term assets	0
Total assets measured at fair value	84,918
Liabilities:
Accrued Liabilities	0
Total liabilities measured at fair value	0
Level 2 [Member]
Assets:
Short-term investments	0
Prepaid expenses and other	200
Other long-term assets	0
Total assets measured at fair value	200
Liabilities:
Accrued Liabilities	159
Total liabilities measured at fair value	159
Level 3 [Member]
Assets:
Short-term investments	0
Prepaid expenses and other	0
Other long-term assets	100
Total assets measured at fair value	100
Liabilities:
Accrued Liabilities	0
Total liabilities measured at fair value	0
Total [Member]
Assets:
Short-term investments	84,918
Prepaid expenses and other	200
Other long-term assets	100
Total assets measured at fair value	85,218
Liabilities:
Accrued Liabilities	159
Total liabilities measured at fair value	$ 159