Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	Apr. 30, 2014	Jan. 31, 2014	Apr. 30, 2013
Assets:
Short-term investments	$ 34,063	$ 33,099
Fair Value, Measurements, Recurring
Assets:
Total	59,273	56,049	20,040
Liabilities:
Total	22,488	21,027	18,726
Fair Value, Measurements, Recurring | Level 1
Assets:
Total	58,501	55,646	19,828
Liabilities:
Total	22,478	20,854	18,615
Fair Value, Measurements, Recurring | Level 2
Assets:
Total	772	403	212
Liabilities:
Total	10	173	111
Other Current Assets | Fair Value, Measurements, Recurring
Assets:
Available-for-sale securities	687	576	287
Hedge derivatives	772	403	212
Other Current Assets | Fair Value, Measurements, Recurring | Level 1
Assets:
Available-for-sale securities	687	576	287
Other Current Assets | Fair Value, Measurements, Recurring | Level 2
Assets:
Hedge derivatives	772	403	212
Short-term investments | Fair Value, Measurements, Recurring
Assets:
Short-term investments	34,063	33,099
Short-term investments | Fair Value, Measurements, Recurring | Level 1
Assets:
Short-term investments	34,063	33,099
Other non-current assets | Fair Value, Measurements, Recurring
Assets:
SERP assets - employer	1,273	1,117	926
SERP assets - employee	22,478	20,854	18,615
Other non-current assets | Fair Value, Measurements, Recurring | Level 1
Assets:
SERP assets - employer	1,273	1,117	926
SERP assets - employee	22,478	20,854	18,615
Other non-current liabilities | Fair Value, Measurements, Recurring
Liabilities:
SERP liabilities - employee	22,478	20,854	18,615
Other non-current liabilities | Fair Value, Measurements, Recurring | Level 1
Liabilities:
SERP liabilities - employee	22,478	20,854	18,615
Accrued Liabilities | Fair Value, Measurements, Recurring
Liabilities:
Hedge derivatives	10	173	111
Accrued Liabilities | Fair Value, Measurements, Recurring | Level 2
Liabilities:
Hedge derivatives	$ 10	$ 173	$ 111