Income/Loss Per Share - Common Stock (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Numerator
Net income (loss)	$ (301)	$ 16,602	$ (15,260)	$ 40,340	$ 93,420	$ 40,806	$ 37,141	$ 35,220	$ 41,381	$ 206,587	$ 254,127
Weighted-average common shares outstanding:
Basic (in shares)									58,574	57,840	52,798
Assumed conversion of employee stock options (in shares)									841	1,242	2,291
Assumed conversion of Platinum Warrant (in shares)									0	0	3,551
Diluted									59,415	59,082	58,640
Net income (loss) per basic share:
Net income (loss) (in dollars per share)	$ (0.01)	$ 0.28	$ (0.26)	$ 0.69	$ 1.60	$ 0.70	$ 0.64	$ 0.61	$ 0.71	$ 3.57	$ 4.81
Net income (loss) per diluted share:
Net income (loss) (in dollars per share)	$ (0.01)	$ 0.28	$ (0.26)	$ 0.68	$ 1.58	$ 0.69	$ 0.63	$ 0.60	$ 0.70	$ 3.50	$ 4.33