Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Costs and expenses:
Research and development expenses	$ 13,598	$ 28,247	$ 54,954	$ 83,944
General and administrative expenses	3,366	6,448	23,798	21,038
Restructuring expenses		809		809
Total costs and expenses	16,964	35,504	78,752	105,791
Loss from continuing operations	(16,964)	(35,504)	(78,752)	(105,791)
Other income and expenses:
Interest income	250	64	646	258
Interest expense	(1,659)	(1,560)	(30,400)	(20,708)
Gain on deconsolidation of Silver Creek Pharmaceuticals, Inc.	10,848		10,848
Gain on sale of asset			1,703
Other income (expense), net	69	385	(592)	278
Net loss from continuing operations before income tax benefit	(7,456)	(36,615)	(96,547)	(125,963)
Income tax benefit	2,133	9,770	32,372	9,770
Net loss from continuing operations	(5,323)	(26,845)	(64,175)	(116,193)
Discontinued operations:
Income (loss) from discontinued operations, net of tax	8,456	(3,430)	547,994	(3,698)
Net income (loss)	3,133	(30,275)	483,819	(119,891)
Net income (loss) attributable to non-controlling interest	31	(207)	(1,160)	(600)
Net income (loss) attributable to Merrimack Pharmaceuticals, Inc.	3,102	(30,068)	484,979	(119,291)
Other comprehensive income (loss):
Unrealized loss on available-for-sale securities		(3)		(2)
Other comprehensive loss		(3)		(2)
Comprehensive income (loss)	3,102	(30,071)	484,979	(119,293)
Amounts attributable to Merrimack Pharmaceuticals, Inc.:
Net loss from continuing operations	(5,354)	(26,638)	(63,015)	(115,593)
Income (loss) from discontinued operations, net of tax	8,456	(3,430)	547,994	(3,698)
Net income (loss) attributable to Merrimack Pharmaceuticals, Inc.	$ 3,102	$ (30,068)	$ 484,979	$ (119,291)
Basic and dilutive net income (loss) per common share
Net loss from continuing operations	$ (0.40)	$ (2.06)	$ (4.77)	$ (9.33)
Net income (loss) from discontinued operations, net of tax	0.64	(0.27)	41.52	(0.30)
Net income (loss) per share	$ 0.24	$ (2.33)	$ 36.75	$ (9.63)
Weighted-average common shares used per share calculations—basic and diluted	13,282	12,921	13,197	12,383
Cash dividend paid per common share			$ 10.55