Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Mar. 31, 2019
Current assets:
Cash and cash equivalents	$ 117,970	$ 121,021
Short-term marketable securities	309,569	370,677
Accounts receivable, net	100,994	90,809
Inventories	91,193	80,942
Prepaid expenses and other current assets	16,850	13,748
Total current assets	636,576	677,197
Long-term marketable securities	167,981	21,718
Property and equipment, net	162,060	145,005
Goodwill	32,594	32,601
In-process research and development	15,205	15,208
Long-term deferred tax assets, net	47,028	77,502
Other assets	135,167	85,115
Total assets	1,196,611	1,054,346
Current liabilities:
Accounts payable	31,566	32,185
Accrued expenses	71,876	57,420
Deferred revenue	19,156	16,393
Other current liabilities	3,661
Total current liabilities	126,259	105,998
Contingent consideration	10,440	9,575
Long-term deferred tax liabilities	822	822
Other long-term liabilities	12,227	1,061
Total liabilities	149,748	117,456
Commitments and contingencies (Note 13)
Stockholders' equity:
Class B Preferred Stock, $.01 par value Authorized - 1,000,000 shares; Issued and outstanding - none
Common stock, $.01 par value Authorized - 100,000,000 shares; Issued - 47,498,385 shares at December 31, 2019 and 47,026,226 shares at March 31, 2019	451	451
Additional paid in capital	733,054	690,507
Retained earnings	570,683	399,473
Treasury stock at cost - 2,385,550 shares at December 31, 2019 and 1,903,241 shares at March 31, 2019	(240,330)	(138,852)
Accumulated other comprehensive loss	(16,995)	(14,689)
Total stockholders' equity	1,046,863	936,890
Total liabilities and stockholders' equity	$ 1,196,611	$ 1,054,346