Balance Sheet Information - Summary of Securities with Gross Unrealized Loss Positions and Fair Values (Detail) - USD ($) $ in Thousands	Aug. 31, 2017	Feb. 28, 2017
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	$ 50,330	$ 63,606
Less Than 12 Months, Unrealized Losses	(138)	(285)
12 Months or Greater, Fair Value	7,537	731
12 Months or Greater, Unrealized Losses	(26)	(12)
Total, Fair Value	57,867	64,337
Total, Unrealized Losses	(164)	(297)
Asset-backed securities
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	5,809	6,086
Less Than 12 Months, Unrealized Losses	(13)	(28)
12 Months or Greater, Fair Value	0	0
12 Months or Greater, Unrealized Losses	0	0
Total, Fair Value	5,809	6,086
Total, Unrealized Losses	(13)	(28)
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	30,297	35,095
Less Than 12 Months, Unrealized Losses	(88)	(140)
12 Months or Greater, Fair Value	3,000	0
12 Months or Greater, Unrealized Losses	(7)	0
Total, Fair Value	33,297	35,095
Total, Unrealized Losses	(95)	(140)
Foreign government bonds
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value		650
Less Than 12 Months, Unrealized Losses		(1)
12 Months or Greater, Fair Value		0
12 Months or Greater, Unrealized Losses		0
Total, Fair Value		650
Total, Unrealized Losses		(1)
Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	1,914	3,204
Less Than 12 Months, Unrealized Losses	(6)	(22)
12 Months or Greater, Fair Value	131	0
12 Months or Greater, Unrealized Losses	0	0
Total, Fair Value	2,045	3,204
Total, Unrealized Losses	(6)	(22)
U.S. government agency securities
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	7,817	11,306
Less Than 12 Months, Unrealized Losses	(22)	(65)
12 Months or Greater, Fair Value	4,008	731
12 Months or Greater, Unrealized Losses	(16)	(12)
Total, Fair Value	11,825	12,037
Total, Unrealized Losses	(38)	(77)
U.S. government notes
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	4,493	7,265
Less Than 12 Months, Unrealized Losses	(9)	(29)
12 Months or Greater, Fair Value	398	0
12 Months or Greater, Unrealized Losses	(3)	0
Total, Fair Value	4,891	7,265
Total, Unrealized Losses	$ (12)	$ (29)