Collaboration Revenue - Summary of Deferred Revenue (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Dec. 31, 2011
Deferred Revenue Arrangement [Line Items]
Current portion of deferred revenue	$ 7,398	$ 9,963	$ 1,402
Long-term portion of deferred revenue	59,994	48,673	15,519
Deferred revenue	67,392	58,636
Upfront and Milestone Payments [Member]
Deferred Revenue Arrangement [Line Items]
Deferred revenue	65,846	51,359
Prepaid Research and Development Services [Member]
Deferred Revenue Arrangement [Line Items]
Deferred revenue	1,502	7,229
Other [Member]
Deferred Revenue Arrangement [Line Items]
Deferred revenue	$ 44	$ 48

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.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 605

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SAB TOPIC 13.A.4(a).Q1)

-URI http://asc.fasb.org/extlink&oid=27012821&loc=d3e214044-122780

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section 45

-Paragraph 8

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6935-107765

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 13

-Section A

Name:	us-gaap_DeferredRevenueNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant