Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 132,526	$ 54,126
Short-term investments	250,928	257,221
Accounts receivable, net	38,000	31,658
Inventories, net	48,569	41,411
Prepaid expenses and other current assets	7,946	6,694
Total current assets	477,969	391,110
Long-term investments	25,871	60,047
Fixed assets, net	108,670	107,046
Goodwill	62,040	55,197
Equity investment	14,146	14,146
Other assets	657	825
Total assets	689,353	628,371
Current liabilities:
Accounts payable	14,368	14,658
Accrued expenses	45,865	41,057
Convertible senior notes	338	324
Current portion of deferred revenue	0	102
Income taxes payable	90	76
Total current liabilities	60,661	56,217
Convertible senior notes	290,592	276,173
Other liabilities	16,874	16,498
Total liabilities	368,127	348,888
Commitments and contingencies
Stockholders’ equity:
Preferred stock, par value $0.001; 5,000,000 shares authorized; none issued and outstanding at December 31, 2018 and 2017	0	0
Common stock, par value $0.001; 250,000,000 shares authorized; 41,222,799 shares issued and outstanding at December 31, 2018; 40,668,877 shares issued and outstanding at December 31, 2017	41	41
Additional paid-in capital	709,691	669,032
Accumulated deficit	(388,226)	(389,136)
Accumulated other comprehensive loss	(280)	(454)
Total stockholders’ equity	321,226	279,483
Total liabilities and stockholders’ equity	$ 689,353	$ 628,371

Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

Name:	us-gaap_AccountsPayableCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount due from customers or clients, within one year of the balance sheet date (or the normal operating cycle, whichever is longer), for goods or services (including trade receivables) that have been delivered or sold in the normal course of business, reduced to the estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.