Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating activities:
Cash provided by (used in) operating activities - continuing operations	$ (2,272)	$ 23,155
Cash used in operating activities - discontinued operations		(4,131)
Net cash provided by (used in) operating activities	(2,272)	19,024
Investing activities:
Purchases of investments		(427)
Proceeds from sale of investments		2,474
Purchases of property, plant and equipment	(17)	(44)
Proceeds from sale of property, plant and equipment		258
Cash provided by (used in) investing activities - continuing operations	(17)	2,261
Cash provided by investing activities - discontinued operations		5,892
Net cash provided by (used in) investing activities	(17)	8,153
Financing activities:
Payment of withholding taxes on exercise of restricted stock units		(122)
Purchases of treasury stock	(4,985)	(184)
Cash used in financing activities - continuing operations	(4,985)	(306)
Cash used in financing activities - discontinued operations		(754)
Net cash used in financing activities	(4,985)	(1,060)
Increase (decrease) in cash and cash equivalents	(7,274)	26,117
Cash and cash equivalents, beginning of the period	37,128	60,980
Cash and cash equivalents, end of the period	29,854	87,097
Less cash and cash equivalents of discontinued operations at the end of the period	0	34,270
Cash and cash equivalents of continuing operations, end of the period	$ 29,854	52,827
Non-cash investing and financing activities:
Issuance of common stock for vested restricted stock units		$ 1,476