Computation of Earnings Per Common Share - Basic and Diluted Earnings Calculation (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 27, 2019	Jul. 28, 2018	Jul. 27, 2019	Jul. 28, 2018
Basic earnings per unit
Net income	$ 29,896	$ 29,900	$ 44,175	$ 47,131
Weighted-average number of common shares (in shares)	31,487,011	31,206,340	31,469,401	31,198,349
Basic earnings per common share (in dollars per share)	$ 0.95	$ 0.96	$ 1.40	$ 1.51
Diluted earnings per unit
Weighted-average number of common shares (in shares)	31,487,011	31,206,340	31,469,401	31,198,349
Potential common stock arising from stock options, and unvested restricted share units (in shares)	333,285	627,477	333,967	615,014
Potential shares of common stock issuable on exercise of convertible senior notes	0	120,196
Total shares-diluted (in shares)	31,820,296	31,954,013	31,803,368	32,180,960
Diluted earnings per common share (in dollars per share)	$ 0.94	$ 0.94	$ 1.39	$ 1.46
Anti-dilutive weighted shares excluded from the calculation of earnings per share (in shares)	10,287,752	9,941,638	10,307,698	9,698,425
Stock-based awards
Diluted earnings per unit
Anti-dilutive weighted shares excluded from the calculation of earnings per share (in shares)	276,284	50,366	296,230	54,554
Convertible senior notes
Diluted earnings per unit
Anti-dilutive weighted shares excluded from the calculation of earnings per share (in shares)	5,005,734	4,885,538	5,005,734	4,638,137
Warrants
Diluted earnings per unit
Anti-dilutive weighted shares excluded from the calculation of earnings per share (in shares)	5,005,734	5,005,734	5,005,734	5,005,734