Discontinued Operations (Summary Of Financial Information That Has Been Segregated From Continuing Operations (Details) - USD ($) $ in Thousands	3 Months Ended				12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Discontinued operations:
Net loss from discontinued operations	$ (1,385)	$ 937	$ (6,404)	$ 9,595	$ 2,743	$ (9,891)	$ (44,683)
Assets:
Assets held for sale	118,470				118,470	121,218
Discontinued Operations, Held-for-sale | Consumer and Industrial Chemistry Technologies
Discontinued operations:
Revenue					72,344	73,992	74,599
Operating expenses					(65,940)	(63,621)	(62,673)
Depreciation and amortization					(2,760)	(2,391)	(2,257)
Research and development					(590)	(515)	(1)
Income (loss) from operations					3,054	7,465	9,668
Other income (expense)					341	(284)	127
Income (loss) before income taxes					3,395	7,181	9,795
Income tax benefit (expense)					(652)	(2,730)	(3,441)
Net loss from discontinued operations					2,743	4,451	6,354
Assets:
Accounts receivable, net	10,547				10,547	11,121
Inventories	52,069				52,069	43,299
Other current assets	446				446	88
Property and equipment, net	15,899				15,899	16,049
Goodwill	19,480				19,480	19,480
Other intangible assets, net	20,029				20,029	26,183
Assets held for sale	118,470				118,470	116,220
Liabilities:
Accounts payable	8,883				8,883	11,654
Accrued liabilities	291				291	796
Liabilities held for sale	$ 9,174				$ 9,174	12,450
Discontinued Operations, Held-for-sale | Drilling Technologies
Discontinued operations:
Revenue						11,534	27,627
Cost of revenue						(7,309)	(18,667)
Selling, general and administrative						(6,963)	(15,285)
Depreciation and amortization						0	(1,714)
Research and development						(5)	(64)
Gain (loss) on disposal of long-lived assets						97	103
Impairment of inventory and long-lived assets						0	(36,522)
Income (loss) from operations						(2,646)	(44,522)
Other income (expense)						(96)	(412)
Loss on sale of businesses						(1,600)	(1,199)
Loss on write-down of assets held for sale						(6,831)	(18,971)
Income (loss) before income taxes						(11,173)	(65,104)
Income tax benefit (expense)						4,138	23,661
Net loss from discontinued operations						(7,035)	(41,443)
Discontinued Operations, Held-for-sale | Production Technologies
Discontinued operations:
Revenue						4,002	8,292
Cost of revenue						(3,236)	(7,881)
Selling, general and administrative						(1,759)	(3,790)
Depreciation and amortization						0	(584)
Research and development						(364)	(888)
Gain (loss) on disposal of long-lived assets						0	(50)
Impairment of inventory and long-lived assets						0	(3,913)
Income (loss) from operations						(1,357)	(8,814)
Other income (expense)						(52)	(96)
Loss on sale of businesses						(479)	0
Loss on write-down of assets held for sale						(9,718)	(6,161)
Income (loss) before income taxes						(11,606)	(15,071)
Income tax benefit (expense)						4,299	5,477
Net loss from discontinued operations						$ (7,307)	$ (9,594)