Consolidated Statement of Cash Flows Statement $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Net income (loss)	$ 127,454	$ (158,486)	$ 46,982
Income (loss) from discontinued operations, net of income taxes	10,506	(241,968)	(22,513)
Income from continuing operations, net of income taxes	116,948	83,482	69,495
Depreciation and amortization	7,813	8,832	10,461
Stock-based compensation expense	6,332	2,810	3,712
Provision for deferred income taxes	3,570	3,498	(21,561)
Non-cash reserve for potential bad debts	0	5,967	0
Net loss (gain) on disposal of assets	319	(1,019)	502
Accounts receivable	(21,603)	17,919	(3,835)
Inventories	(6,359)	(6,715)	(7,416)
Other current assets	(1,358)	(2,366)	4,605
Accounts payable	18,957	3,220	1,866
Other current liabilities and accrued expenses	2,169	(9,500)	(5,135)
Income taxes	356	17,994	11,085
Net cash provided by operating activities from continuing operations	127,144	124,122	63,779
Net cash (used in) provided by operating activities from discontinued operations	(7,857)	(19,413)	13,383
Net cash provided by operating activities	119,287	104,709	77,162
Purchases of marketable securities	(763)	(30,172)	(6,432)
Proceeds from sale of marketable securities	7,884	21,095	14,835
Proceeds from the sale of assets	0	0	(156)
Acquisitions, net of cash acquired	0	(128)	(57,138)
Purchases of property and equipment	(6,821)	(4,014)	(3,449)
Net cash provided by (used in) investing activities from continuing operations	300	(13,219)	(52,340)
Net cash used in investing activities from discontinued operations	0	(46)	(2,656)
Net cash provided by (used in) investing activities	300	(13,265)	(54,996)
Settlement of performance stock units	0	0	(11,198)
Purchase and retirement of common stock	0	(50,000)	(25,000)
Proceeds from exercise of stock options	2,175	4,476	15,830
Other financing activities	(4)	(4)	(2)
Net cash provided by (used in) financing activities from continuing operations	2,171	(45,528)	(20,370)
Net cash used in financing activities from discontinued operations	(29)	(14)	(13,686)
Net cash provided by (used in) financing activities	2,142	(45,542)	(34,056)
EFFECT OF CURRENCY TRANSLATION ON CASH	(1,932)	(1,467)	(950)
INCREASE (DECREASE ) IN CASH AND CASH EQUIVALENTS	119,797	44,435	(12,840)
CASH AND CASH EQUIVALENTS, beginning of period	169,720	125,285	138,125
CASH AND CASH EQUIVALENTS, end of period	289,517	169,720	125,285
Less cash and cash equivalents from discontinued operations	7,564	11,277	3,884
Cash and cash equivalents	281,953	158,443	121,401
Cash paid for interest	173	361	234
Cash paid for income taxes	5,647	7,161	5,241
Cash received for refunds of income taxes	2,232	5,377	7,261
Cash held in banks outside the United States	$ 230,168	$ 116,259	$ 44,573