Consolidated Statements of Cash Flows $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
OPERATING ACTIVITIES
Net income	$ 810,287	$ 72,921	$ 74,183
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and other	49,089	47,827	46,266
Stock-based compensation expense	21,019	13,252	11,709
Impairment loss	0	1,481	0
Amortization of debt discount and deferred issuance costs	771	1,582	3,952
Change in fair value of acquisition contingencies	1,405	1,467	1,114
Accretion of interest on deferred consideration	6,569	8,224	10,000
Amortization of inventory step-up to fair value	0	0	3,650
Net change in operating lease right-of-use assets and liabilities	434	3,964	0
Right-of-use assets	100,544	92,119
Change in deferred tax assets and liabilities	(20,211)	(1,742)	(20,458)
Change in fair value of derivative liabilities - Convertible Senior Notes	1,084	0	0
Loss on extinguishment of debt	10,384	748	8,262
Increase (Decrease) in Operating Capital
Accounts receivable	(402,094)	(36,059)	8,236
Inventories	(54,903)	9,143	(3,974)
Prepaid expenses and other current and non-current assets	(14,264)	4,314	(12,681)
Accounts payable	52,226	2,434	(331)
Accrued payroll and related expenses	16,024	(1,037)	1,674
Increase (Decrease) in Income Taxes Payable	137,708	4,175	2,082
Other current and non-current liabilities	14,235	1,791	2,661
Net cash provided by operating activities	629,763	134,485	136,345
INVESTING ACTIVITIES
Acquisitions of property, equipment and intangibles	(64,927)	(27,229)	(31,689)
Proceeds from government assistance allocated to fixed assets	1,605	0	0
Proceeds from sale of Summers Ridge Property	0	0	146,644
Net cash (used for) provided by investing activities	(63,322)	(27,229)	114,955
FINANCING ACTIVITIES
Proceeds from issuance of common stock	9,613	14,782	17,047
Payments of debt issuance costs	0	0	(513)
Payments on finance lease obligation	(511)	(371)	(130)
Payments on Revolving Credit Facility	0	(53,188)	(40,000)
Repurchases of common stock	(47,889)	(10,728)	(4,344)
Payments on acquisition contingent consideration	(6,044)	(4,044)	(6,303)
Payments of deferred consideration	(42,000)	(44,000)	(46,000)
Payment on Convertible Senior Note and Derivative Liability	(43,446)	0	0
Payments of Term Loan	0	0	(161,813)
Transaction costs related to debt exchange	0	(733)	(2,002)
Net cash used for financing activities	(130,277)	(98,282)	(244,058)
Effect of exchange rate changes on cash	1,002	106	367
Net increase in cash and cash equivalents	437,166	9,080	7,609
Cash and cash equivalents, beginning of period	52,775	43,695	36,086
Cash and cash equivalents, at end of period	489,941	52,775	43,695
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION
Cash paid during the period for interest	480	2,295	7,929
Cash paid during the period for income taxes	109,912	2,189	6,923
Purchase of property, equipment and intangibles by incurring current liabilities	7,160	1,040	1,785
Accrued receivable for capital expenditures to be reimbursed under a government contract	15,854
Reduction of other current liabilities upon issuance of restricted share units	767	2,018	0
Extinguishment of Convertible Senior Notes through issuance of stock	7,230	86,428	200,219
Principal amount of Term Loan exchanged for Revolving Credit Facility	$ 0	$ 0	$ 83,187