Collaboration Agreements - Deferred Revenue (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Deferred Revenue Arrangement [Line Items]
Deferred revenue, Current	$ 33,862	$ 33,862
Deferred revenue, Long-term		8,465
Total	33,862	42,327
Astellas [Member]
Deferred Revenue Arrangement [Line Items]
Deferred revenue, Current	33,862	33,862
Deferred revenue, Long-term		$ 8,465

The carrying amount of consideration received or receivable as of the balance sheet date on potential earnings that were not recognized as revenue in conformity with GAAP, and which are expected to be recognized as such within one year or the normal operating cycle, if longer, including sales, license fees, and royalties, but excluding interest income.

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The noncurrent portion of deferred revenue amount as of balance sheet date. Deferred revenue is a liability related to a revenue producing activity for which revenue has not yet been recognized, and is not expected to be recognized in the next twelve months. Generally, an entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP.

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