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, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Discontinued operations:
Net loss from discontinued operations	$ (722)	$ 319	$ (2,704)	$ (11,235)	$ (17,836)	$ (876)	$ (2,169)	$ (30,156)	$ (14,342)	$ (51,037)	$ (20,620)
Assets:
Assets held for sale	0				43,900				0	43,900
Discontinued Operations, Held-for-sale | Drilling Technologies
Discontinued operations:
Revenue									11,534	27,627	52,112
Cost of revenue									(7,309)	(18,667)	(35,410)
Selling, general and administrative									(6,963)	(15,285)	(21,049)
Depreciation and amortization									0	(1,714)	(3,240)
Research and development									(5)	(64)	(202)
Gain (loss) on disposal of long-lived assets									97	103	17
Impairment of inventory and long-lived assets									0	(36,522)	(19,568)
Loss from operations									(2,646)	(44,522)	(27,340)
Other expense									(96)	(412)	(259)
Loss on sale of businesses									(1,600)	(1,199)	0
Loss on write-down of assets held for sale									(6,831)	(18,971)	0
Loss before income taxes									(11,173)	(65,104)	(27,599)
Income tax benefit									4,138	23,661	9,675
Net loss from discontinued operations									(7,035)	(41,443)	(17,924)
Assets:
Accounts receivable, net	0				5,072				0	5,072
Inventories	0				9,078				0	9,078
Other current assets	0				278				0	278
Long-term receivable	0				0				0	0
Property and equipment, net	0				11,277				0	11,277
Goodwill	0				15,333				0	15,333
Other intangible assets, net	0				7,395				0	7,395
Assets held for sale	0				48,433				0	48,433
Valuation allowance	0				(18,971)				0	(18,971)
Assets held for sale, net	0				29,462				0	29,462
Liabilities:
Accounts payable	0				2,472				0	2,472
Accrued liabilities	0				1,190				0	1,190
Liabilities held for sale	0				3,662				0	3,662
Discontinued Operations, Held-for-sale | Production Technologies
Discontinued operations:
Revenue									4,002	8,292	12,281
Cost of revenue									(3,236)	(7,881)	(10,179)
Selling, general and administrative									(1,759)	(3,790)	(4,158)
Depreciation and amortization									0	(584)	(658)
Research and development									(364)	(888)	(596)
Gain (loss) on disposal of long-lived assets									0	(50)	3
Impairment of inventory and long-lived assets									0	(3,913)	(804)
Loss from operations									(1,357)	(8,814)	(4,111)
Other expense									(52)	(96)	(40)
Loss on sale of businesses									(479)	0	0
Loss on write-down of assets held for sale									(9,718)	(6,161)	0
Loss before income taxes									(11,606)	(15,071)	(4,151)
Income tax benefit									4,299	5,477	1,455
Net loss from discontinued operations									(7,307)	(9,594)	$ (2,696)
Assets:
Accounts receivable, net	0				1,784				0	1,784
Inventories	0				8,115				0	8,115
Other current assets	0				370				0	370
Long-term receivable	0				4,179				0	4,179
Property and equipment, net	0				3,978				0	3,978
Goodwill	0				1,689				0	1,689
Other intangible assets, net	0				484				0	484
Assets held for sale	0				20,599				0	20,599
Valuation allowance	0				(6,161)				0	(6,161)
Assets held for sale, net	0				14,438				0	14,438
Liabilities:
Accounts payable	0				914				0	914
Accrued liabilities	0				385				0	385
Liabilities held for sale	$ 0				$ 1,299				$ 0	$ 1,299