Income/Loss Per Share - Common Stock (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								9 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2017	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Numerator
Net income (loss)	$ 2,433	$ 18,641	$ 12,849	$ 220,606	$ 52,914	$ 12,278	$ (4,998)	$ (12,205)		$ 254,529	$ 47,989	$ (53,629)
Weighted-average common shares outstanding:
Weighted Average Number of Shares Issued, Basic										52,798	46,552	46,004
Assumed conversion of employee stock options (in shares)										2,291	2,235	0
Assumed conversion of Platinum Warrant (in shares)										3,551	6,602	0
Weighted-average shares outstanding (diluted)		58,640							46,004		55,389
Net income (loss) per basic share:
Net income (loss) (in dollars per share)	$ 0.04	$ 0.33	$ 0.26	$ 4.66	$ 1.13	$ 0.26	$ (0.11)	$ (0.26)		$ 4.82	$ 1.03	$ (1.17)
Net income (loss) per diluted share:
Net income (loss) (in dollars per share)	$ 0.04	$ 0.32	$ 0.22	$ 3.82	$ 0.93	$ 0.22	$ (0.11)	$ (0.26)		$ 4.34	$ 0.87	$ (1.17)