Long-Term Debt (Details 2) (USD $)			0 Months Ended			1 Months Ended	3 Months Ended				0 Months Ended		1 Months Ended		1 Months Ended		0 Months Ended				0 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Sep. 09, 2011 2% Senior Convertible Notes Due 2017	Mar. 24, 2009 2% Senior Convertible Notes Due 2017	Mar. 26, 2007 2% Senior Convertible Notes Due 2017	Mar. 31, 2009 2% Senior Convertible Notes Due 2017	Jun. 30, 2013 2% Senior Convertible Notes Due 2017	Mar. 31, 2009 2% Senior Convertible Notes Due 2017	Sep. 30, 2013 2% Senior Convertible Notes Due 2017	Mar. 26, 2007 2% Senior Convertible Notes Due 2017 Viropharma Common Stock	Sep. 09, 2011 Credit Facility	Sep. 30, 2013 Credit Facility	Sep. 30, 2011 Credit Facility Maximum	Sep. 09, 2011 Credit Facility Maximum	Sep. 30, 2011 Credit Facility Minimum	Sep. 09, 2011 Credit Facility Minimum	Sep. 09, 2011 Credit Facility London Interest Bank Offer Rate Maximum	Sep. 09, 2011 Credit Facility London Interest Bank Offer Rate Minimum	Sep. 09, 2011 Credit Facility Alternate Base Rate Maximum	Sep. 09, 2011 Letters of Credit	Sep. 09, 2011 Letters of Credit Alternate Base Rate Minimum	Sep. 09, 2011 Swing line Loans
Debt disclosures
Face amount of debt issued					$ 250,000,000						$ 200,000,000
Stated interest rate (as a percent)					2.00%				2.00%
Net proceeds from issuance of convertible notes					241,800,000
Interest payment terms					payable semi-annually in arrears on March 15 and September 15 of each year commencing on September 15, 2007.
Fair value of convertible debt					148,100,000				440,600,000
Reduction in carrying value of debt securities					101,900,000
Interest expense on convertible debt securities at effective rates (as a percent)					8.00%
Conversion price of senior convertible notes (in dollars per share)					$ 18.87
Number of business days during which the convertible debt may be converted after a required number of consecutive trading days					5 days
Senior secured leverage ratio														3.50		2.00
Number of consecutive trading days required before the debt may be converted					5 days
Percentage of price per note less than the last reported sale price of common stock for each trading day					98.00%
Common stock trading days			20 days
Consecutive common stock trading days			30 days
Percentage of excess conversion price in effect on last trading day			130.00%
Number of trading days during which reporting entity may elect option to irrevocably elect to settle conversions in cash					35 days
Exercise price of warrants per share sold to receive shares of common stock (in dollars per share)					$ 24.92					$ 14.24
Transactions cost on purchase of call options and warrants sold					23,300,000
Common stock received by call options (in shares)					13,250,000
Number of trading days for expiry of warrants					60 days
Percentage of warrant exercise price higher than the price per share					75.00%
Shares of reporting entity's preferred stock owed to counterparties if market price of common stock exceeds strike price of warrants					13,250,000
Additional percentage of preferred stock convertible for common stock under the warrants					10.00%
Repurchase of senior convertible notes				45,000,000
Total consideration for repurchase of senior convertible notes				21,200,000
Percentage of outstanding senior convertible notes on repurchase				18.00%
Percentage of par value price executed on senior convertible debt outstanding				47.00%
Number of call options sold (in shares)				2,380,000
Proceeds from sale of call options				1,800,000
Warrants repurchased (in shares)				2,380,000
Payments for repurchase of warrants				1,500,000
Gain on extinguishment of debt								9,100,000
Common stock entitled to be received (in shares)						10,870,000
Potential shares owed to counterparties				10,870,000
Value of notes outstanding that correlate to potential shares owed to counterparties						205,000,000
Accrued interest payable									200,000			200,000
Capitalized debt issuance costs									4,800,000			1,700,000
Unamortized debt issuance costs	1,848,000	2,551,000							1,300,000			500,000
Principal balance outstanding									205,000,000
Carrying value of convertible debt	168,467,000	161,793,000							168,500,000
Face value of converted notes							12,000
Shares issued to convertible note holders							634
Maximum borrowing capacity																				20,000,000		10,000,000
Credit facility term											3 years
Interest coverage ratio																3.50
Variable interest rate margin (as a percent)																	2.75%	2.25%	1.75%		1.25%
Line of credit facility, commitment fee (as a percent)													0.45%		0.35%
Amount of cash and availability under credit agreement subject to minimum liquidity covenant												$ 100,000,000				$ 100,000,000