Grifols Collaboration Agreement - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jul. 31, 2009	Sep. 26, 2015	Sep. 27, 2014	Sep. 28, 2013
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration agreements revenue		$ 253.1	$ 223.3	$ 197.9
Grifols [Member] | Collaboration Agreement [Member] | 2012-2013 [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Share of revenue from assay that includes test for HCV	47.00%
Grifols [Member] | Collaboration Agreement [Member] | 2014 [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Share of revenue from assay that includes test for HCV	48.00%
Grifols [Member] | Collaboration Agreement [Member] | 2015 [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Share of revenue from assay that includes test for HCV	50.00%
Blood screening [Member] | Grifols [Member] | Collaboration Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Manufacturing costs entitled to recover	50.00%
Share of revenue from assay that excludes test for HCV	50.00%