Stock Option Plans - Additional Information (Detail) (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Jan. 31, 2014	Dec. 31, 2013	Jan. 31, 2013	Jan. 31, 2012
Stock Based Compensation [Line Items]
Compensation expense related to stock-based awards granted	$ 1,143,000		$ 1,586,000	$ 1,331,000
Weighted average grant-date fair value of options granted	$ 14.63		$ 8.10	$ 6.44
Associated excess tax benefit	(5,000)	420,000	420,000	778,000
Contractual term of stock options granted and outstanding	5 years 7 months 13 days
Intrinsic value of options exercised	1,053,000		2,529,000
Fair value of options vested	601,000		1,268,000	1,195,000
Options vested	79
Total unrecognized compensation expense related to unvested stock options	542,000
Expense expected to be recognized over weighted average period	1 year 1 month 6 days
Exercise of options	498,000		329,000	2,809,000
Restricted Stock [Member]
Stock Based Compensation [Line Items]
Expense expected to be recognized over weighted average period	10 months 24 days
Total unrecognized compensation expense related to unvested restricted stock awards	$ 573,000
2006 Plan [Member]
Stock Based Compensation [Line Items]
Vesting period of stock options granted and outstanding	3 years
Contractual term of stock options granted and outstanding	10 years
Shares available for grant	871
1994 Plan [Member]
Stock Based Compensation [Line Items]
Vesting period of stock options granted and outstanding	3 years
Contractual term of stock options granted and outstanding	10 years
1998 Plan [Member]
Stock Based Compensation [Line Items]
Vesting period of stock options granted and outstanding	3 years
Contractual term of stock options granted and outstanding	10 years
2000 Plan [Member]
Stock Based Compensation [Line Items]
Vesting period of stock options granted and outstanding	3 years
Contractual term of stock options granted and outstanding	10 years
Director Plan [Member]
Stock Based Compensation [Line Items]
Vesting period of stock options granted and outstanding	1 year
Contractual term of stock options granted and outstanding	10 years