Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 219,720	$ 349,462
Short-term investments	116,629	0
Accounts and notes receivable, net of allowance of $1,577 and $1,882 as of June 30, 2019 and December 31, 2018, respectively	134,630	130,579
Contract assets, net	26,648	13,960
Inventory	40,999	33,763
Prepaid expenses and other current assets	36,429	30,391
Total current assets	575,055	558,155
Property and equipment, net of accumulated depreciation of $42,822 and $39,885 as of June 30, 2019 and December 31, 2018, respectively	40,500	37,893
Deferred income tax assets, net	20,658	19,347
Intangible assets, net	14,424	15,935
Goodwill	24,969	24,981
Long-term notes receivable, net of current portion	35,170	40,230
Other assets	35,594	22,999
Total assets	746,370	719,540
Current liabilities:
Accounts payable	9,064	15,164
Accrued liabilities	34,011	41,092
Contract with customer, liability, current	113,351	107,016
Other current liabilities	3,852	37
Total current liabilities	163,673	166,011
Deferred revenue, net of current portion	74,586	74,417
Liability for unrecognized tax benefits	3,462	2,849
Long-term deferred compensation	3,755	3,235
Other long-term liabilities	11,967	5,704
Total liabilities	257,443	252,216
Commitments and contingencies (Note 12)
Stockholders’ equity:
Preferred stock, $0.00001 par value; 25,000,000 shares authorized; no shares issued and outstanding as of June 30, 2019 and December 31, 2018	0	0
Common stock, $0.00001 par value; 200,000,000 shares authorized; 59,251,731 and 58,810,637 shares issued and outstanding as of June 30, 2019 and December 31, 2018, respectively	1	1
Additional paid-in capital	467,904	453,400
Treasury stock at cost, 20,220,227 shares as of June 30, 2019 and December 31, 2018	(155,947)	(155,947)
Retained earnings	178,540	171,383
Accumulated other comprehensive loss	(1,571)	(1,513)
Total stockholders’ equity	488,927	467,324
Total liabilities and stockholders’ equity	746,370	719,540
Current portion of deferred revenue
Current liabilities:
Contract with customer, liability, current	113,351	107,016
Customer deposits
Current liabilities:
Contract with customer, liability, current	$ 3,395	$ 2,702