Components of Convertible Notes (Detail) - USD ($) $ in Thousands		May 31, 2017	Feb. 28, 2017
Debt Instrument [Line Items]
Net carrying amount		$ 751,173	$ 745,633	[1]
0.25% Convertible Senior Notes due 2019 | Unsecured Debt
Debt Instrument [Line Items]
Liability component: Principal		805,000	805,000
Less: debt issuance costs		(6,769)	(7,442)
Less: debt discount		(47,058)	(51,925)
Net carrying amount		751,173	745,633
Equity component	[2]	$ 96,890	$ 96,890

[1] Derived from audited financial statements.

[2] Recorded in the Consolidated Balance Sheets in Additional paid-in capital.