Commitments and Contingencies (Collaborative Arrangements) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
In-licensing arrangements
Research and development	$ 933.4	[1]	$ 953.0	[1]	$ 764.5	[1]
In-licensing Arrangement | Research Collaboration with Santaris
In-licensing arrangements
Maximum conditional obligation	71.0
Milestones payment	1.5		3.0		2.5
Support costs	4.5		8.1		5.3
In-licensing Arrangement | Collaboration and Licensse Agreement with Sangamo
In-licensing arrangements
Upfront payment			13.0
Maximum conditional obligation	213.5
Research and development	15.2		8.9		0
Out-licensing Arrangement
Out-licensing arrangements
Milestone payments received	3.0		18.3		11.5
Out-licensing Arrangement | Other Revenues
Out-licensing arrangements
Milestone revenues recognized	5.0		19.4		17.5
Out-licensing Arrangement | Product Sales
Out-licensing arrangements
Milestone revenues recognized	58.3		83.8		65.2
Out-licensing Arrangement | Development Milestone
Out-licensing arrangements
Maximum milestone payment receivable	39.0
Out-licensing Arrangement | Sales Milestone
Out-licensing arrangements
Maximum milestone payment receivable	$ 71.5

[1] Research and development (“R&D”) includes intangible asset impairment charges of $19.9 million (2012: $71.2 million, 2011: $16.0 million) for the year to December 31, 2013. Selling, general and administrative (“SG&A”) costs include amortization and impairment charges of intangible assets relating to intellectual property rights acquired of $152.0 million for the year to December 31, 2013 (2012: $280.3 million, 2011: $145.0 million).