Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash Flows from Operating Activities
Net income (loss)	$ (567)	$ (18,530)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation and amortization	7,724	8,796
Non-cash interest expense	3,320	3,081
Deferred income taxes	115	(15)
Share-based compensation expense	3,646	3,157
Changes in operating assets and liabilities:
Accounts receivable and contract assets	(27,846)	(8,134)
Inventories and deferred cost of sales	2,446	8,489
Prepaid expenses and other current assets	(1,480)	(2,457)
Accounts payable and accrued expenses	14,459	(12,260)
Customer deposits and deferred revenue	(5,242)	(3,855)
Income taxes receivable and payable, net	124	(463)
Other, net	905	(100)
Net cash provided by (used in) operating activities	(2,396)	(22,291)
Cash Flows from Investing Activities
Capital expenditures	(1,070)	(2,180)
Proceeds from the sale of investments	71,130	22,500
Payments for purchases of investments	(34,866)	(41,258)
Net cash provided by (used in) investing activities	35,194	(20,938)
Cash Flows from Financing Activities
Proceeds (net of tax withholdings) from option exercises and employee stock purchase plan	956	1,021
Restricted stock tax withholdings	(680)	(642)
Net cash provided by (used in) financing activities	276	379
Effect of exchange rate changes on cash and cash equivalents	(48)	11
Net increase (decrease) in cash, cash equivalents, and restricted cash	33,026	(42,839)
Cash, cash equivalents, and restricted cash - beginning of period	129,951	213,082
Cash, cash equivalents, and restricted cash - end of period	162,977	170,243
Supplemental Disclosure of Cash Flow Information
Interest paid	4,681	4,693
Income taxes paid	293	2,341
Non-cash operating and financing activities
Net transfer of property, plant and equipment to inventory	$ 526	130
Right-of-use assets obtained in exchange for lease obligations		$ 238