CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (USD $) In Thousands, except Share data	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning Balance at Dec. 31, 2011	$ 220,141	$ 158	$ 776,946		$ (556,963)
Beginning Balance (in shares) at Dec. 31, 2011		157,608,702
Issuance of shares pursuant to ARIAD stock plans (in shares)		3,661,213
Issuance of shares pursuant to ARIAD stock plans	10,511	3	10,508
Issuance of common stock from warrant exercise (in shares)	5,805,843	5,805,843
Issuance of common stock from warrant exercise	87,046	6	87,040
Stock-based compensation	20,341		20,341
Payments of tax withholding obligations related to stock compensation	(4,336)		(4,336)
Net loss	(220,872)				(220,872)
Other comprehensive income (loss)	20			20
Ending Balance at Dec. 31, 2012	112,851	167	890,499	20	(777,835)
Ending Balance (in shares) at Dec. 31, 2012		167,075,758
Issuance of shares pursuant to ARIAD stock plans (in shares)		2,330,429
Issuance of shares pursuant to ARIAD stock plans	6,284	2	6,282
Issuance of common stock, net of issuance costs (in shares)		16,489,893
Issuance of common stock, net of issuance costs	310,037	17	310,020
Stock-based compensation	35,421		35,421
Payments of tax withholding obligations related to stock compensation	(3,363)		(3,363)
Net loss	(274,158)				(274,158)
Other comprehensive income (loss)	(1,555)			(1,555)
Ending Balance at Dec. 31, 2013	185,517	186	1,238,859	(1,535)	(1,051,993)
Ending Balance (in shares) at Dec. 31, 2013		185,896,080
Issuance of shares pursuant to ARIAD stock plans (in shares)		1,398,014
Issuance of shares pursuant to ARIAD stock plans	3,694	1	3,693
Equity component of convertible debt issuance	25,255		25,255
Stock-based compensation	32,403		32,403
Payments of tax withholding obligations related to stock compensation	(816)		(816)
Net loss	(162,602)				(162,602)
Other comprehensive income (loss)	(2,650)			(2,650)
Ending Balance at Dec. 31, 2014	$ 80,801	$ 187	$ 1,299,394	$ (4,185)	$ (1,214,595)
Ending Balance (in shares) at Dec. 31, 2014		187,294,094