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Fair Value Measurements - Amortized Cost and Fair Market Value of Securities by Contractual Maturity (Details) - USD ($)
$ in Thousands
Feb. 02, 2019
Feb. 03, 2018
Jan. 28, 2017
Amortized Cost      
Mature in one year or less $ 50,350 $ 31,500  
Mature after one year through five years 8,883 25,451  
Total 59,233 56,951  
Fair Market Value      
Mature in one year or less 50,317 31,474  
Mature after one year through five years 8,867 25,335  
Fair Market Value 59,184 56,809  
Changes among the fair value levels      
Changes between Level 1 to Level 2, Assets 0 0 $ 0
Changes between Level 2 to Level 1, Assets $ 0 $ 0 $ 0