Debt - Additional Information (Detail) - Roche Credit Facility [Member] - USD ($)			6 Months Ended
	Jul. 31, 2017	Aug. 02, 2016	Jun. 30, 2017
Line Of Credit Facility [Line Items]
Credit facility, borrowing capacity		$ 100,000,000
Credit facility, quarterly commitment fee percentage on available balance, payable during draw period		0.30%
Credit facility, draw period		3 years
Credit facility, interest rate		5.00%
Credit facility, covenants description			The Roche Credit Facility contains certain affirmative covenants, including, among others, obligations for the Company to provide monthly and annual financial statements, to meet specified minimum cash requirements, to provide tax gross-up and indemnification protection, and to comply with laws. The Roche Credit Facility also contains certain negative covenants, including, among others, restrictions on the Company’s ability to dispose of certain assets, to acquire another company or business, to encumber or permit liens on certain assets, to incur additional indebtedness (subject to customary exceptions), and to pay dividends on the Company’s common stock. The Company was in compliance with its covenants under the Roche Credit Facility as of June 30, 2017.
Credit facility, events of default			$ 0
Credit facility, outstanding balances			$ 0
Foreign Subsidiaries [Member]
Line Of Credit Facility [Line Items]
Equity interest percentage held		65.00%
Subsequent Event
Line Of Credit Facility [Line Items]
Credit facility, borrowing capacity	$ 200,000,000
Credit facility, available borrowing capacity	$ 80,000,000
Credit facility, quarterly commitment fee percentage on available balance, payable during draw period	0.40%
Credit facility, draw period	4 years
Credit facility, interest rate	6.50%
Credit facility, payments description	The Company shall pay Roche quarterly during the Draw Period and for six months thereafter accrued interest on the outstanding principal of the loans. Beginning six months after the Draw Period and for five years thereafter, the Company shall pay Roche quarterly equal payments of principal, with accrued interest, in arrears until maturity of the Roche Credit Facility on February 2, 2026 (the “Final Maturity Date”).
Credit facility, frequency of periodic payment	quarterly
Credit facility, maturity date	Feb. 02, 2026
Subsequent Event | Achievement of Certain Milestones [Member]
Line Of Credit Facility [Line Items]
Credit facility, remaining borrowing capacity	$ 70,000,000
Subsequent Event | Achievement of Certain Additional Milestones [Member]
Line Of Credit Facility [Line Items]
Credit facility, remaining borrowing capacity	$ 50,000