Summary of Business and Significant Accounting Policies (Computation of Basic and Diluted Loss Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended																12 Months Ended
	Jan. 31, 2017		Oct. 31, 2016		Jul. 31, 2016		Apr. 30, 2016		Jan. 31, 2016		Oct. 31, 2015		Jul. 31, 2015		Apr. 30, 2015		Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2015
Accounting Policies [Abstract]
Net income	$ (4,985)		$ 23,998		$ 6,885		$ (3,138)		$ (5,726)		$ 6,003		$ 7,450		$ (3,178)		$ 22,760	$ 4,549	$ 849
Weighted-average shares — basic																	15,067	14,914	14,756
Dilutive effect of equity incentive plans																	199	204	231
Weighted-average shares — diluted																	15,266	15,118	14,987
Basic	$ (0.33)	[1]	$ 1.59	[1]	$ 0.46	[1]	$ (0.21)	[1]	$ (0.38)	[1]	$ 0.40	[1]	$ 0.50	[1]	$ (0.21)	[1]	$ 1.51	$ 0.31	$ 0.06
Diluted	$ (0.33)	[1]	$ 1.57	[1]	$ 0.45	[1]	$ (0.21)	[1]	$ (0.38)	[1]	$ 0.39	[1]	$ 0.49	[1]	$ (0.21)	[1]	$ 1.49	$ 0.30	$ 0.06

[1] Net loss per share was calculated based on basic shares outstanding due to the anti-dilutive effect on the inclusion of common stock equivalent shares.