Income Taxes - Additional Information (Detail) (USD $)	3 Months Ended								12 Months Ended			401 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013
Income Taxes [Line Items]
Operating loss carryforwards, beginning of expiration year									2014
Operating loss carryforwards, ending of expiration year									2033
Operating loss carryforwards from exercises of stock options	$ 11,600,000								$ 11,600,000			$ 11,600,000
Deferred tax assets, gross	133,573,000				114,127,000				133,573,000	114,127,000		133,573,000
Net change in valuation allowance for deferred tax assets									19,400,000	(2,700,000)
Research and development cost	25,076,000	21,087,000	12,984,000	13,762,000	12,834,000	10,914,000	13,849,000	14,805,000	72,909,000	52,402,000	66,862,000	458,577,000
Sarepta International C.V. [Member]
Income Taxes [Line Items]
Research and development cost									46,700,000
Federal
Income Taxes [Line Items]
Net operating loss carryforwards	260,900,000								260,900,000			260,900,000
State
Income Taxes [Line Items]
Net operating loss carryforwards	$ 237,700,000								$ 237,700,000			$ 237,700,000