Equity (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended										3 Months Ended
	Apr. 30, 2013		Apr. 30, 2012		Apr. 30, 2013 Common Stock	Apr. 30, 2012 Common Stock	Apr. 30, 2013 Class A Common Stock	Jan. 31, 2013 Class A Common Stock	Apr. 30, 2012 Class A Common Stock	Jan. 31, 2012 Class A Common Stock	Apr. 30, 2013 Capital in Excess of Par Value	Apr. 30, 2012 Capital in Excess of Par Value	Apr. 30, 2013 Retained Earnings	Apr. 30, 2012 Retained Earnings	Apr. 30, 2013 Treasury Stock	Apr. 30, 2012 Treasury Stock	Apr. 30, 2013 Accumulated Other Comprehensive Income		Apr. 30, 2012 Accumulated Other Comprehensive Income		Apr. 30, 2013 Noncontrolling Interests		Apr. 30, 2012 Noncontrolling Interests
Components Of Stockholders Equity [Line Items]
Beginning Balance	$ 425,692		$ 394,074		$ 264	$ 261	$ 66	$ 66	$ 66	$ 66	$ 159,696	$ 153,331	$ 272,094	$ 251,695	$ (110,701)	$ (111,909)	$ 102,271		$ 97,922		$ 2,002		$ 2,708
Net income	8,179		6,761										8,210	6,633							(31)		128
Dividends declared	(1,272)		(13,826)										(1,272)	(13,826)
Stock repurchase	(467)														(467)
Stock options exercised, net of tax benefit of $350	(603)		429		2	1					555	428			(1,160)
Supplemental executive retirement plan	6		22								6	22
Stock-based compensation expense	572		481								572	481
Net unrealized gain on investments	1		23														1		23
Stock donation			2,164									725				1,439
Foreign currency translation adjustments	(5,235)	[1]	3,563	[1]													(5,197)	[1]	3,500	[1]	(38)	[1]	63	[1]
Ending Balance	$ 426,873		$ 393,691		$ 266	$ 262	$ 66	$ 66	$ 66	$ 66	$ 160,829	$ 154,987	$ 279,032	$ 244,502	$ (112,328)	$ (110,470)	$ 97,075		$ 101,445		$ 1,933		$ 2,899

[1] The currency translation adjustment is not adjusted for income taxes to the extent that they relate to permanent investments in international subsidiaries.