Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Revenues:
Product revenues, net	$ 9,968
License and collaboration revenues	11,313	$ 14,842
Total revenues	21,281	14,842
Costs and expenses:
Cost of product revenues	711
Research and development expenses	32,882	35,679
Selling, general and administrative expenses	17,795	9,189
Total costs and expenses	51,388	44,868
Loss from operations	(30,107)	(30,026)
Other income and expenses
Interest income	72	47
Interest expense	(8,580)	(4,566)
Other (expense) income, net	(43)	113
Net loss	(38,658)	(34,432)
Net (loss) income attributable to non-controlling interest	(185)	327
Net loss attributable to Merrimack Pharmaceuticals, Inc.	(38,473)	(34,759)
Other comprehensive (loss) income:
Unrealized (loss) gain on available-for-sale securities	(14)	47
Other comprehensive (loss) income	(14)	47
Comprehensive loss	$ (38,487)	$ (34,712)
Net loss per share available to common stockholders-basic and diluted	$ (0.33)	$ (0.32)
Weighted-average common shares used in computing net loss per share available to common stockholders-basic and diluted	116,064	107,148