Acquisition of Pharmasset, Inc. Other Costs as Classifed by Expense Category (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2012	Jun. 30, 2011
Other Costs Classified by Expense Category [Line Items]
Total other costs	$ 1,100	$ 52,278	$ 29,011	$ 17,500
Transaction Costs			10,166
Research and Development Expense [Member]
Other Costs Classified by Expense Category [Line Items]
Total other costs		0	7,478
Selling, General and Administrative Expenses [Member]
Other Costs Classified by Expense Category [Line Items]
Total other costs			14,200
Transaction Costs		28,461
Interest Expense [Member]
Other Costs Classified by Expense Category [Line Items]
Total other costs			$ 7,333