Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash Flows from Operating Activities
Net income (loss)	$ (34,095)	$ (253,461)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation and amortization	17,315	32,306
Non-cash interest expense	6,219	5,771
Deferred income taxes	10	(27,658)
Share-based compensation expense	7,745	9,441
Asset impairment		252,343
Changes in operating assets and liabilities:
Accounts receivable and contract assets	6,227	(39,655)
Inventories and deferred cost of sales	8,534	(9,890)
Prepaid expenses and other current assets	(3,957)	4,868
Accounts payable and accrued expenses	(25,955)	11,761
Customer deposits and deferred revenue	11,294	(38,573)
Income taxes receivable and payable, net	(587)	(4,189)
Other, net	(891)	(504)
Net cash provided by (used in) operating activities	(8,141)	(57,440)
Cash Flows from Investing Activities
Capital expenditures	(6,441)	(3,796)
Proceeds from the sale of investments	40,500	45,365
Payments for purchases of investments	(76,108)	(65,400)
Net cash provided by (used in) investing activities	(42,049)	(23,831)
Cash Flows from Financing Activities
Cash withholdings for employee stock purchase plan	1,784	2,039
Restricted stock tax withholdings	(2,241)	(2,859)
Purchases of common stock		(1,225)
Net cash provided by (used in) financing activities	(457)	(2,045)
Effect of exchange rate changes on cash and cash equivalents	13
Net increase (decrease) in cash, cash equivalents, and restricted cash	(50,634)	(83,316)
Cash, cash equivalents, and restricted cash - beginning of period	213,082	280,583
Cash, cash equivalents, and restricted cash - end of period	162,448	197,267
Supplemental Disclosure of Cash Flow Information
Interest paid	4,721	4,692
Income taxes paid	2,618	3,563
Non-cash operating and financing activities
Net transfer of inventory to property, plant and equipment	3,695	$ 6
Right-of-use assets obtained in exchange for lease obligations	$ 339