CONSOLIDATED STATEMENTS OF CASH FLOWS Non-Cash Activities - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other Significant Noncash Transactions [Line Items]
Unrealized gain (loss) on available-for-sale securities	$ 342	$ (19)	$ (207)
Net change in accounts payable and accrued expenses related to purchases of property and equipment	3,490	4,363	(103)
Earnout liability recorded for Adesis acquisition			1,670
Excess tax benefits accrued for in other current liabilities			(4,232)
Cash paid for income tax	17,771	23,248	12,870
Common Stock Issued to Board of Directors and Scientific Advisory Board that was Earned and Accrued for in Previous Period [Member]
Other Significant Noncash Transactions [Line Items]
Other significant noncash transaction, value of consideration received	$ 300	300	300
Common Stock Issued to Employees that was Earned and Accrued for in Previous Period Net of Shares Withheld for Taxes [Member]
Other Significant Noncash Transactions [Line Items]
Other significant noncash transaction, value of consideration received		$ 174	$ 1,105