Acquisitions (Tables)

9 Months Ended

Sep. 30, 2012

Business Acquisition [Line Items]

Schedule of Acquisition Related Costs

Acquisition-related costs for the three and nine months endedSeptember 30, 2012 and 2011 include the following:

	Three months ended					Nine months ended
	September 30,					September 30,
	2012			2011		2012		2011
Separately-identifiable employee costs	$	457		$	—	$	3,552	$	6,597
Professional fees	1,052			—		11,562		3,450
Changes in fair value of contingent consideration	(542		)	236		4,333		1,117
	$	967		$	236	$	19,447	$	11,164

Enobia Pharma Corp. [Member]

Business Acquisition [Line Items]

Schedule of Purchase Price Allocation

A reconciliation of upfront payments in accordance with the purchase agreement to the total purchase price is presented below:

	Enobia
Base payment per agreement	$	610,000
Cash acquired	18,141
Working capital adjustment	(4,265		)
Upfront payment in accordance with agreement	623,876
Estimated fair value of contingent consideration	117,000
Total purchase price	$	740,876

Schedule of Recognized Identified Assets Acquired and Liabilities Assumed

The fair values of acquired assets and liabilities are based on preliminary estimates and are subject to change. The following table summarizes the estimated fair values of assets acquired and liabilities assumed:

	Enobia
Cash and cash equivalents	$	18,141
Current assets	5,536
In-process research and development	587,000
Other noncurrent assets	910
Assets acquired	611,587
Deferred tax liability	(31,665		)
Other liabilities assumed	(13,246		)
Liabilities assumed	(44,911		)
Goodwill	174,200
Net assets acquired	$	740,876

Business Acquisition, Pro Forma Information

The following unaudited pro forma information presents the combined results of operations for the three months endedSeptember 30, 2011 and for the nine months endedSeptember 30, 2012 and 2011 as if the acquisition of Enobia had been completed on January 1, 2011. The pro forma results do not reflect operating efficiencies or potential cost savings which may result from the consolidation of operations. The pro forma results have been adjusted to remove costs associated with changes in the fair value of Enobia's preferred stock. Included in the pro forma net income for the nine months endedSeptember 30, 2012, are approximately $20,600 and $7,900 of Alexion and Enobia acquisition-related costs, respectively, which are not expected to have an ongoing impact.

	Three months ended		Nine months ended
	September 30,		September 30,
	2011		2012		2011
Revenues	$	204,047	$	813,588	$	555,872
Net income	50,567		155,437		91,592
Earnings per common share
Basic	$	0.28	$	0.82	$	0.50
Diluted	$	0.26	$	0.79	$	0.48