Significant Accounting Policies (Details 3) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
Mar. 31, 2013 item	Dec. 31, 2012 item
Consolidation of variable interest entities
Number of variable interest entities in which the entity is not primary beneficiary	5	6
Carrying value of investments in variable interest entities	$ 47.5
Maximum
Equity method of accounting
Ownership percentage	20.00%
Regulus Therapeutics Inc. \| Maximum
Equity method of accounting
Ownership percentage	20.00%

Carrying amount of the assets in the reporting entity's statement of financial position that relate to the reporting entity's variable interest in the Variable Interest Entity (VIE), where the reporting entity is not the VIE's primary beneficiary.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 50

-Paragraph 4

-Subparagraph a

-URI http://asc.fasb.org/extlink&oid=7880789&loc=d3e5728-111685

Name:	us-gaap_VariableInterestEntityNonconsolidatedCarryingAmountAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant