Nature of Operations (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		12 Months Ended
	Apr. 30, 2017	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Liquidity
Net loss attributable to common shareholders		$ 24,065	$ 11,780	$ 57,600	$ 55,800	$ 88,600
Accumulated deficit		1,078,541		1,051,467
Net cash used in operating activities		23,859	6,916
Net loss attributable to the Company		(24,039)	(11,754)
Noncash gains		7,000
Cash and cash equivalents		11,765	66,882	46,014	$ 63,961
Net working capital		10,400		$ 44,400
Net cash used in investing activities		(786)	23,396
Remaining lease payment		$ 48,413
Proceeds from exercise of warrants			$ 109
Subsequent event
Liquidity
Net proceeds from public offering	$ 18,200
Proceeds from exercise of warrants	$ 18,400