Restructuring Charges (Details) - USD ($) $ in Thousands	3 Months Ended					6 Months Ended	9 Months Ended
	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Jun. 30, 2016	Sep. 30, 2016	Sep. 30, 2015
Restructuring Cost and Reserve [Line Items]
Balance at the beginning of the period	$ 11	$ 100	$ 955	$ 1,053	$ 1,185	$ 11	$ 11	$ 1,185
Accrued		1,395		179	604
Adjustments			(78)
Paid		(1,484)	(777)	(277)	(736)
Balance at the end of the period	11	11	$ 100	955	1,053	11	11	$ 100
Reduction in workforce (as a percentage)			20.00%					20.00%
Modification of stock options related to executive retirement								$ 389
Modification of stock options related to restructuring activities								479
Research And Development Expense [Member]
Restructuring Cost and Reserve [Line Items]
Modification of stock options related to executive retirement								384
Modification of stock options related to restructuring activities								384
Research And Development Expense [Member] | Contract Termination [Member]
Restructuring Cost and Reserve [Line Items]
Balance at the beginning of the period			$ 571	706	1,185			1,185
Accrued
Adjustments			(78)
Paid			(493)	(135)	(479)
Balance at the end of the period				571	706
Research And Development Expense [Member] | Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Balance at the beginning of the period		32	180	265
Accrued		588		57	522
Adjustments
Paid		(620)	(148)	(142)	(257)
Balance at the end of the period			32	180	265			32
General And Administrative Expense [Member]
Restructuring Cost and Reserve [Line Items]
Modification of stock options related to executive retirement								95
Modification of stock options related to restructuring activities								95
General And Administrative Expense [Member] | Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Balance at the beginning of the period	11	68	204	82		11	11
Accrued		807		122	82
Adjustments
Paid		(864)	(136)
Balance at the end of the period		$ 11	$ 68	$ 204	$ 82		$ 11	$ 68