Condensed Consolidated Statement of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Market offering	Common Stock	Common Stock Market offering	Additional Paid-in Capital	Additional Paid-in Capital Market offering	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Balance (in shares) at Jun. 30, 2017			171,308
Balance at Jun. 30, 2017	$ 11,727		$ 171		$ 930,293		$ (76)	$ (918,661)
Increase (Decrease) in Stockholders' Equity
Shares issued for cash under employee share plans, net (in shares)			3,703
Shares issued for cash under employee share plans	18,274		$ 3		18,271
Share-based compensation expense	13,538				13,538
Issuance of common stock, net of offering costs (in shares)			24,070	2,554
Issuance of common stock, net of offering costs	243,018	$ 40,340	$ 24	$ 3	242,994	$ 40,337
Change in unrealized loss on marketable securities	(681)						(681)
Net loss	(94,898)							(94,898)
Extinguishment of 2020 notes (in shares)			7,956
Extinguishment of 2020 Notes	(15,697)		$ 8		(15,705)
Conversion of 2020 Notes (in shares)			913
Conversion of 2020 Notes	5,419		$ 1		5,418
Issuance of 2024 Notes	44,110				44,110
Balance (in shares) at Mar. 31, 2018			210,504
Balance at Mar. 31, 2018	265,150		$ 210		1,279,256		(757)	(1,013,559)
Balance (in shares) at Jun. 30, 2017			171,308
Balance at Jun. 30, 2017	11,727		$ 171		930,293		(76)	(918,661)
Increase (Decrease) in Stockholders' Equity
Net loss								(147,300)
Balance (in shares) at Jun. 30, 2018			211,290
Balance at Jun. 30, 2018	219,743		$ 211		1,286,000		(461)	(1,066,007)
Balance (in shares) at Dec. 31, 2017			207,458
Balance at Dec. 31, 2017	242,182		$ 207		1,233,359		(676)	(990,708)
Increase (Decrease) in Stockholders' Equity
Shares issued for cash under employee share plans, net (in shares)			816
Shares issued for cash under employee share plans	3,671		$ 1		3,670
Share-based compensation expense	4,719				4,719
Issuance of common stock, net of offering costs (in shares)				2,230
Issuance of common stock, net of offering costs		37,510		$ 2		37,508
Change in unrealized loss on marketable securities	(81)						(81)
Net loss	(22,851)							(22,851)
Balance (in shares) at Mar. 31, 2018			210,504
Balance at Mar. 31, 2018	265,150		$ 210		1,279,256		(757)	(1,013,559)
Balance (in shares) at Jun. 30, 2018			211,290
Balance at Jun. 30, 2018	219,743		$ 211		1,286,000		(461)	(1,066,007)
Increase (Decrease) in Stockholders' Equity
Shares issued for cash under employee share plans, net (in shares)			3,008
Shares issued for cash under employee share plans	13,734		$ 3		13,731
Share-based compensation expense	18,663				18,663
Issuance of common stock, net of offering costs (in shares)				7,250
Issuance of common stock, net of offering costs		122,526		$ 7		122,519
Change in unrealized loss on marketable securities	626						626
Net loss	(73,667)							(73,667)
Balance (in shares) at Mar. 31, 2019			221,548
Balance at Mar. 31, 2019	301,625		$ 221		1,440,913		165	(1,139,674)
Balance (in shares) at Dec. 31, 2018			217,860
Balance at Dec. 31, 2018	285,351		$ 218		1,387,422		(109)	(1,102,180)
Increase (Decrease) in Stockholders' Equity
Shares issued for cash under employee share plans, net (in shares)			2,091
Shares issued for cash under employee share plans	11,414		$ 1		11,413
Share-based compensation expense	8,321				8,321
Issuance of common stock, net of offering costs (in shares)				1,597
Issuance of common stock, net of offering costs		$ 33,759		$ 2		$ 33,757
Change in unrealized loss on marketable securities	274						274
Net loss	(37,494)							(37,494)
Balance (in shares) at Mar. 31, 2019			221,548
Balance at Mar. 31, 2019	$ 301,625		$ 221		$ 1,440,913		$ 165	$ (1,139,674)