CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2018	Mar. 31, 2018
Current assets:
Cash and cash equivalents	$ 76,382	$ 42,975
Short-term marketable securities	334,064	319,274
Accounts receivable, net	74,201	70,010
Inventories	63,656	50,204
Prepaid expenses and other current assets	13,296	11,808
Total current assets	561,599	494,271
Long-term marketable securities		37,502
Property and equipment, net	134,065	117,167
Goodwill	33,719	35,808
In-process research and development	15,730	16,705
Long-term deferred tax assets, net	116,248	70,746
Other assets	25,804	14,176
Total assets	887,165	786,375
Current liabilities:
Accounts payable	21,884	23,565
Accrued expenses	46,099	46,147
Deferred revenue	13,996	14,970
Total current liabilities	81,979	84,682
Other long-term liabilities	889	776
Contingent consideration	10,493	10,490
Long-term deferred tax liabilities	850	903
Total liabilities	94,211	96,851
Commitments and contingencies (Note 11)
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 - 46,935,424 shares at September 30, 2018 and 46,100,649 shares at March 31, 2018 Outstanding - 45,038,453 shares at September 30, 2018 and 44,375,337 shares at March 31, 2018	450	444
Additional paid in capital	660,132	619,905
Retained earnings	280,650	140,457
Treasury stock at cost - 1,896,971 shares at September 30, 2018 and 1,725,312 shares at March 31, 2018	(136,743)	(67,078)
Accumulated other comprehensive loss	(11,535)	(4,204)
Total stockholders' equity	792,954	689,524
Total liabilities and stockholders' equity	$ 887,165	$ 786,375