Basic and Diluted Net Income (Loss) Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Sep. 30, 2019		Sep. 30, 2018		Sep. 30, 2019	Sep. 30, 2018
Numerator:
Net income (loss)	$ (15,260)	[1]	$ 37,141	[1]	$ 25,080	$ 72,361
Weighted-average shares outstanding:
Basic (in shares)	58,528		57,799		58,440	57,570
Assumed conversion of employee stock grants (in shares)	0		1,398		735	1,549
Diluted (in shares)	58,528		59,197		59,175	59,119
Net income (loss) per basic share (in usd per share)	$ (0.26)		$ 0.64		$ 0.43	$ 1.26
Net income (loss) per diluted share (in usd per share)	$ (0.26)		$ 0.63		$ 0.42	$ 1.22
Common stock equivalents that could potentially dilute net income per basic share in the future, but were not included in the computation of diluted earnings per share because the impact would have been antidilutive
Payments of Ordinary Dividends, Common Stock	$ 2,903				$ 5,803	$ 0

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