Summary Of Significant Accounting Policies (Schedule Of Assets And Liabilities Measured At Fair Value On Recurring Basis) (Details) (USD $)	3 Months Ended
	Mar. 31, 2012		Dec. 31, 2011
Summary Of Significant Accounting Policies [Line Items]
Number Of Transfers Between Fair Value Measurement Levels	0
ASSETS
Restricted cash	$ 10,673,000		$ 10,519,000
LIABILITIES
Loss Protection Liability Carried At Fair Value	37,283,000		0
Loss Contingency Accrual , Product Liability, Gross	60,000,000
Fair Value, Measurements, Recurring [Member]
ASSETS
Cash and cash equivalents	73,401,000		99,859,000
Short-term investments	231,225,000		104,206,000
Restricted cash	10,673,000		10,519,000
Deferred compensation plan assets	9,745,000		8,192,000
Embedded derivative	2,441,000	[1]	7,690,000	[1]
Assets, fair value	327,485,000		230,466,000
LIABILITIES
Deferred compensation plan liabilities	9,745,000		8,192,000
Loss Protection Liability Carried At Fair Value	50,366,000	[2]	46,419,000	[2]
Liabilities, fair value	60,111,000		54,611,000
Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
ASSETS
Cash and cash equivalents	12,983,000		61,850,000	[3]
Short-term investments	3,000,000		0	[3]
Restricted cash	10,673,000		10,519,000	[3]
Deferred compensation plan assets	2,143,000		990,000	[3]
Embedded derivative	0	[1]	0	[1],[3]
Assets, fair value	28,799,000		73,359,000	[3]
LIABILITIES
Deferred compensation plan liabilities	2,143,000		990,000	[3]
Loss Protection Liability Carried At Fair Value	0	[2]	0	[2],[3]
Liabilities, fair value	2,143,000		990,000	[3]
Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
ASSETS
Cash and cash equivalents	60,418,000		38,009,000	[3]
Short-term investments	228,225,000		104,206,000	[3]
Restricted cash	0		0	[3]
Deferred compensation plan assets	7,602,000		7,202,000	[3]
Embedded derivative	0	[1]	0	[1],[3]
Assets, fair value	296,245,000		149,417,000	[3]
LIABILITIES
Deferred compensation plan liabilities	7,602,000		7,202,000	[3]
Loss Protection Liability Carried At Fair Value	0	[2]	0	[2],[3]
Liabilities, fair value	7,602,000		7,202,000	[3]
Level 3 [Member]
ASSETS
Embedded derivative	2,441,000		7,691,000
LIABILITIES
Loss Protection Liability Carried At Fair Value	50,366,000		46,419,000
Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
ASSETS
Cash and cash equivalents	0		0
Short-term investments	0		0
Restricted cash	0		0
Deferred compensation plan assets	0		0
Embedded derivative	2,441,000	[1]	7,691,000	[1]
Assets, fair value	2,441,000		7,691,000
LIABILITIES
Deferred compensation plan liabilities	0		0
Loss Protection Liability Carried At Fair Value	50,366,000	[2]	46,419,000	[2]
Liabilities, fair value	50,366,000		46,419,000
Bydureon Member | Level 3 [Member]
ASSETS
Embedded derivative	$ 0

[1] The embedded derivative is associated with the promissory note related to the Revenue Sharing Obligation, or RSO, issued in connection with the Termination Agreement (see Note 6). The embedded derivative represents embedded options which would allow Amylin to discharge all or a portion of the obligation under certain circumstances (see Note 8 for the terms of the RSO). The fair value of the embedded derivative is calculated using a probability weighted expected return method, or PWERM. Significant inputs to the valuation include the following: •Management's estimates of total revenue of exenatide products over the period in which the RSO is to be repaid; •A variety of scenarios under which management estimated the probability that BYDUREONTM (exenatide for extended-release injectable suspension) would be approved by the U.S. Food and Drug Administration , or the FDA, prior to June 30, 2014; •A variety of scenarios under which all exenatide products would be removed from certain geographic markets for safety or efficacy reasons and remain unsalable for four consecutive years.

[2] The loss protection liability arose in connection with the Termination Agreement (see Note 6) and relates to payments required to be made prior to the final transfer of the markets outside the United States from Lilly to Amylin. The maximum that could be paid under the loss protection liability is $60.0 million over the period January 1, 2012 through December 31, 2013. The fair value of the loss protection liability is calculated using a PWERM. Significant inputs to the valuation include the following: •Financial projections for markets outside the United States, or the OUS markets, which were provided to Amylin's management by Lilly; • A variety of scenarios under which management estimated the extent to which these financial projections would be achieved, and the resulting payouts of the amounts that could be made for the twelve months ended December 31, 2012 and 2013. The greatest drivers of variability in this liability are the estimated losses subject to the guarantee and variations in the discount rates used in the valuation.

[3] During 2012, the company changed how it categorizes amounts within the fair value hierarchy and thus, certain amounts now reported as Level 2 fair value instruments at March 31, 2012 were previously shown as Level 1 and have been reclassified.