Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues:
Product revenues, net	$ 53,064	$ 4,328
License and collaboration revenues	87,119	84,930	$ 102,756
Other revenues	4,090
Total revenues	144,273	89,258	102,756
Costs and expenses:
Cost of revenues	6,912	46
Research and development expenses	160,917	160,988	138,495
Selling, general and administrative expenses	80,729	57,795	30,517
Restructuring expenses	5,856
Total costs and expenses	254,414	218,829	169,012
Loss from operations	(110,141)	(129,571)	(66,256)
Other income and expenses:
Interest income	276	99	114
Interest expense	(43,645)	(19,232)	(18,230)
Other (expense) income, net	(8)	917	813
Net loss	(153,518)	(147,787)	(83,559)
Net (loss) income attributable to non-controlling interest	(1,778)	170	(268)
Net loss attributable to Merrimack Pharmaceuticals, Inc.	(151,740)	(147,957)	(83,291)
Other comprehensive income (loss):
Unrealized gain (loss) on available-for-sale securities		74	(50)
Other comprehensive income (loss)		74	(50)
Comprehensive loss	$ (151,740)	$ (147,883)	$ (83,341)
Net loss per share available to common stockholders—basic and diluted	$ (1.21)	$ (1.33)	$ (0.80)
Weighted-average common shares used in computing net loss per share available to common stockholders—basic and diluted	125,334	111,356	104,410