Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands		3 Months Ended		9 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Net sales		$ 442,395	$ 431,795	$ 1,352,839	$ 1,115,842
Cost of sales		316,241	349,692	991,876	882,620
Gross profit		126,154	82,103	360,963	233,222
Selling, general and administrative expenses		42,187	36,772	123,341	100,674
Legal and environmental charges		(5,589)		(5,589)
Profit from operations		89,556	45,331	243,211	132,548
Other income (loss):
Interest income		4,621	2,907	12,159	10,305
Other, net		(3,616)	(686)	(5,107)	(1,917)
Income before income taxes		90,561	47,552	250,263	140,936
Provision for income taxes		16,264	140,764	47,934	167,846
Net income (loss)		$ 74,297	$ (93,212)	$ 202,329	$ (26,910)
Income (loss) per share:
Basic (in dollars per share)		$ 0.44	$ (0.55)	$ 1.20	$ (0.16)
Diluted (in dollars per share)		0.44	(0.55)	1.20	(0.16)
Dividends declared (per share) (in dollars per share)		$ 0.115	$ 0.115	$ 0.345	$ 0.34
Weighted average common shares outstanding:
Basic (in shares)		168,795	168,313	168,679	168,216
Diluted (in shares)	[1]	169,314	168,313	169,247	168,216

[1] Common stock equivalents not included in the computation of diluted earnings per share because the impact would have been anti-dilutive were 0 shares for the three month periods ended December 31, 2017 and 2018, respectively, and 121 shares and 8 shares for the nine months ended December 31, 2017 and 2018, respectively.