Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Taxes [Line Items]
Operating loss carryforwards, beginning of expiration year									2016
Operating loss carryforwards, ending of expiration year									2036
Operating loss carryforwards from exercises of stock options	$ 43,500								$ 43,500
Deferred tax assets	274,086				$ 219,824				274,086	$ 219,824
Net change in valuation allowance for deferred tax assets									54,200	54,100
Increase in warrant valuation									0	0	$ 2,779
Costs incurred	93,816	$ 56,533	$ 62,100	$ 59,702	$ 65,705	$ 51,763	$ 42,107	$ 61,862	272,151	221,437	$ 143,546
Sarepta International C.V. [Member]
Income Taxes [Line Items]
Costs incurred									116,200	$ 87,400
Federal [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	498,500								498,500
State [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	425,400								$ 425,400
Research and Development Credits [Member]
Income Taxes [Line Items]
Research and development credits carryforward, Description									These federal and state research and development credits begin to expire between 2018 and 2036 and between 2016 and 2031, respectively
Research and Development Credits [Member] | Federal [Member]
Income Taxes [Line Items]
Research and development credits carryforward, Amount	30,900								$ 30,900
Research and Development Credits [Member] | Federal [Member] | Minimum [Member]
Income Taxes [Line Items]
Research and development credits carryforward, Expiration period									2018
Research and Development Credits [Member] | Federal [Member] | Maximum [Member]
Income Taxes [Line Items]
Research and development credits carryforward, Expiration period									2036
Research and Development Credits [Member] | State [Member]
Income Taxes [Line Items]
Research and development credits carryforward, Amount	$ 9,700								$ 9,700
Research and Development Credits [Member] | State [Member] | Minimum [Member]
Income Taxes [Line Items]
Research and development credits carryforward, Expiration period									2016
Research and Development Credits [Member] | State [Member] | Maximum [Member]
Income Taxes [Line Items]
Research and development credits carryforward, Expiration period									2031