CONSOLIDATED BALANCE SHEETS (UNAUDITED) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
CURRENT ASSETS:
Cash and cash equivalents	$ 225,048	$ 211,022
Short-term investments	301,549	304,323
Accounts receivable	52,124	43,129
Inventory	68,041	70,000
Other current assets	5,410	6,366
Total current assets	652,172	634,840
PROPERTY AND EQUIPMENT, net of accumulated depreciation of $47,701 and $44,943	80,615	69,739
ACQUIRED TECHNOLOGY, net of accumulated amortization of $117,034 and $111,890	106,208	110,951
OTHER INTANGIBLE ASSETS, net of accumulated amortization of $3,726 and $3,384	13,114	13,456
GOODWILL	15,535	15,535
DEFERRED INCOME TAXES	24,781	24,377
OTHER ASSETS	75,765	64,526
TOTAL ASSETS	968,190	933,424
CURRENT LIABILITIES:
Accounts payable	7,024	10,532
Accrued expenses	27,470	36,057
Deferred revenue	86,296	80,782
Other current liabilities	10,784	5,811
Total current liabilities	131,574	133,182
DEFERRED REVENUE	41,596	41,785
RETIREMENT PLAN BENEFIT LIABILITY	44,747	44,055
OTHER LIABILITIES	34,072	23,896
Total liabilities	251,989	242,918
COMMITMENTS AND CONTINGENCIES (Note 15)
SHAREHOLDERS' EQUITY:
Preferred Stock, par value $0.01 per share, 5,000,000 shares authorized, 200,000 shares of Series A Nonconvertible Preferred Stock issued and outstanding (liquidation value of $7.50 per share or $1,500)	2	2
Common Stock, par value $0.01 per share, 200,000,000 shares authorized, 48,760,311 and 48,681,524 shares issued, and 47,394,663 and 47,319,887 shares outstanding, at March 31, 2019 and December 31, 2018, respectively	488	487
Additional paid-in capital	616,206	617,334
Retained earnings	156,309	129,552
Accumulated other comprehensive loss	(15,520)	(16,234)
Treasury stock, at cost (1,365,648 and 1,361,637 shares at March 31, 2019 and December 31, 2018, respectively)	41,284	40,635
Total shareholders’ equity	716,201	690,506
TOTAL LIABILITIES AND SHAREHOLDERS’ EQUITY	$ 968,190	$ 933,424