Balance Sheet Information - Marketable Securities (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Aug. 31, 2017	Aug. 31, 2016	Aug. 31, 2017	Aug. 31, 2016	Feb. 28, 2017
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 81,109,000		$ 81,109,000		$ 80,192,000
Gross Unrealized Gains	46,000		46,000		20,000
Gross Unrealized Losses	(164,000)		(164,000)		(297,000)
Fair Value	80,991,000		80,991,000		79,915,000
Other than temporary impairment losses, investments, available-for-sale securities			0
Asset-backed securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	9,472,000		9,472,000		9,597,000
Gross Unrealized Gains	9,000		9,000		6,000
Gross Unrealized Losses	(13,000)		(13,000)		(28,000)
Fair Value	9,468,000		9,468,000		9,575,000
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	43,768,000		43,768,000		41,822,000
Gross Unrealized Gains	22,000		22,000		11,000
Gross Unrealized Losses	(94,000)		(94,000)		(140,000)
Fair Value	43,696,000		43,696,000		41,693,000
Foreign government bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	650,000		650,000		650,000
Gross Unrealized Gains	1,000		1,000		0
Gross Unrealized Losses	0		0		(1,000)
Fair Value	651,000		651,000		649,000
Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,404,000		3,404,000		3,324,000
Gross Unrealized Gains	2,000		2,000		0
Gross Unrealized Losses	(7,000)		(7,000)		(22,000)
Fair Value	3,399,000		3,399,000		3,302,000
U.S. government agency securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	13,679,000		13,679,000		12,707,000
Gross Unrealized Gains	6,000		6,000		1,000
Gross Unrealized Losses	(38,000)		(38,000)		(77,000)
Fair Value	13,647,000		13,647,000		12,631,000
U.S. government notes
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	10,136,000		10,136,000		12,092,000
Gross Unrealized Gains	6,000		6,000		2,000
Gross Unrealized Losses	(12,000)		(12,000)		(29,000)
Fair Value	10,130,000		10,130,000		$ 12,065,000
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, gross realized gains	$ 0	$ 700,000		$ 1,100,000
Available-for-sale securities, gross realized losses		$ 0	$ 0	$ 0