Marketable Securities (Details 2) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013		Dec. 31, 2012
Cash and Cash Equivalents [Abstract]
Cash equivalents (Alios)	$ 51,059	[1]	$ 69,983	[1]

[1] Amounts include the assets and liabilities of Vertex’s variable interest entity (“VIE”), Alios BioPharma, Inc. (“Alios”). Vertex’s interests and obligations with respect to the VIE’s assets and liabilities are limited to those accorded to Vertex in its agreement with Alios. See Note C, "Collaborative Arrangements," to these condensed consolidated financial statements for amounts.