Accounts Receivable (Details Textual) In Millions, unless otherwise specified	12 Months Ended		3 Months Ended			3 Months Ended
	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)	Sep. 30, 2012 Spain USD ($)	Dec. 31, 2012 Spain USD ($)	Dec. 31, 2011 Spain USD ($)	Sep. 30, 2012 Portugal USD ($)	Dec. 31, 2012 Portugal USD ($)	Dec. 31, 2011 Portugal USD ($)	Dec. 31, 2012 Italy USD ($)	Dec. 31, 2011 Italy USD ($)	Dec. 31, 2011 Italy EUR (€)
Accounts Receivable (Textual)
Payment terms of accounts receivable arising from product sales	30 to 90 days
Minimum term for accounts receivable	30 days
Maximum term for accounts receivable	90 days
Accounts receivable outstanding for greater than one year	$ 11.8	$ 56.0
Decrease In accounts receivable in Spain			112.0			21.2
Accounts receivable, net				78.9	134.0		24.0	32.9	104.6	68.1
Payment in case of any unfavorable determination received											30.7
Deferred revenue on sales of TYSABRI made in Italy									$ 62.7	$ 13.8