Consolidated Balance Sheets (Current Period Unaudited) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Current assets
Cash and cash equivalents	$ 85,350	$ 85,046
Short-term marketable securities	35,045	46,750
Accounts receivable, net of allowance for doubtful accounts of $939 and $919 as of March 31, 2019 and December 31, 2018, respectively	61,535	59,155
Inventory	9,356	10,087
Prepaid expenses and other current assets	8,613	8,567
Income taxes receivable	2,852	5,757
Total current assets	202,751	215,362
Property and equipment, net	234,211	228,001
Goodwill	128,752	128,752
Other intangible assets, net	18,979	19,850
Long-term marketable securities	18,262	23,579
Operating lease assets	11,965
Other long-term assets	3,676	3,441
Total assets	618,596	618,985
Current liabilities
Accounts payable	16,672	17,411
Accrued compensation	10,129	18,130
Accrued liabilities and other	11,027	16,702
Current operating lease liabilities	3,021
Income taxes payable	594	491
Total current liabilities	41,443	52,734
Long-term operating lease liabilities	9,107
Long-term deferred tax liabilities	20,549	20,162
Other long-term liabilities	4,702	4,592
Total liabilities	75,801	77,488
Shareholders' equity
Preferred stock, $0.001 par value, authorized 10,000,000 shares; issued and outstanding 0 shares as of each of March 31, 2019 and December 31, 2018
Common stock, $0.001 par value, authorized 150,000,000 shares; issued and outstanding 26,846,981 and 26,984,747 shares as of March 31, 2019 and December 31, 2018, respectively	27	27
Additional paid-in capital	259,611	258,502
Retained earnings	291,173	291,460
Accumulated other comprehensive loss	(8,016)	(8,492)
Total shareholders' equity	542,795	541,497
Total liabilities and shareholders' equity	$ 618,596	$ 618,985